Three-dimensional memory device with separated source-side lines and method of making the same

ABSTRACT

A three-dimensional memory device includes an alternating stack of insulating layers and electrically conductive layers located over at least one source layer, and groups of memory opening fill structures vertically extending through the alternating stack. Each memory opening fill structure can include a vertical stack of memory elements and a vertical semiconductor channel. A plurality of source-side select gate electrodes can be laterally spaced apart by source-select-level dielectric isolation structures. Alternatively or additionally, the at least one source layer may include a plurality of source layers. A group of memory opening fill structures can be selected by selecting a source layer and/or by selecting a source-level electrically conductive layer.

FIELD

The present disclosure relates generally to the field of semiconductor devices, and particular to a three-dimensional memory device including separated source-side select lines and/or separated source lines and methods of manufacturing the same.

BACKGROUND

Three-dimensional vertical NAND strings having one bit per cell are disclosed in an article by T. Endoh et al., titled “Novel Ultra High Density Memory With A Stacked-Surrounding Gate Transistor (S-SGT) Structured Cell”, IEDM Proc. (2001) 33-36.

SUMMARY

According to yet another aspect of the present disclosure, a three-dimensional memory device is provided, which comprises: an alternating stack of insulating layers and electrically conductive layers located over a plurality of source layers, wherein the alternating stack is located between a pair of backside trench fill structures; groups of memory openings vertically extending through the alternating stack; and groups of memory opening fill structures located in the groups of memory openings, wherein each of the memory opening fill structures includes a respective vertical stack of memory elements, a respective vertical semiconductor channel having a first end that contacts a respective one of the plurality of source layers, and a respective drain region contacting a second end of the respective vertical semiconductor channel, wherein: the plurality of source layers are laterally spaced apart and electrically isolated from each other; and each group of memory opening fill structures contacts a respective one of the plurality of source layers.

According to still another aspect of the present disclosure, a method of forming a three-dimensional memory device, comprising: forming an alternating stack of insulating layers and spacer material layers over a substrate, wherein the spacer material layers are formed as, or are subsequently replaced with, electrically conductive layers; forming groups of memory openings through the alternating stack; forming groups of memory opening fill structures in the memory openings, wherein each of the group of memory opening fill structures includes a respective vertical stack of memory elements and a respective vertical semiconductor channel; forming a source-level material layer by thinning the substrate, by removing the substrate, or by replacing the substrate with at least one electrically conductive material layer; and forming a plurality of source layers by patterning the source-level material layer, wherein the plurality of source layers are laterally spaced apart and electrically isolated from each other, wherein each group of memory opening fill structures contacts a respective one of the plurality of source layers.

According to an aspect of the present disclosure, a three-dimensional memory device is provided, which comprises: an alternating stack of insulating layers and electrically conductive layers located over at least one source layer and located between a pair of backside trench fill structures; groups of memory openings vertically extending through the alternating stack; and groups of memory opening fill structures located in the groups of memory openings, wherein each of the memory opening fill structures includes a respective vertical stack of memory elements, a respective vertical semiconductor channel having a first end that contacts the at least one source layer, and a respective drain region contacting a second end of the respective vertical semiconductor channel; wherein the electrically conductive layers comprise: word lines continuously laterally extending between, and contacting, each of the pair of the backside trench fill structures; and a plurality of source-side select gate electrodes located between the at least one source layer and the word lines in a vertical direction, and located between the pair of backside trench fill structures in a horizontal direction, wherein the plurality of source-side select gate electrodes are laterally spaced apart by source-select-level dielectric isolation structures.

According to another aspect of the present disclosure, a method of forming a three-dimensional memory device is provided, which comprises: forming an alternating stack of insulating layers and spacer material layers over a substrate, wherein the spacer material layers are formed as, or are subsequently replaced with, electrically conductive layers; forming groups of memory openings through the alternating stack; forming groups of memory opening fill structures in the memory openings, wherein each of the group of memory opening fill structures includes a respective vertical stack of memory elements, a respective vertical semiconductor channel, and a respective drain region; forming a source-level material layer by thinning the substrate or by replacing the substrate with at least one conductive material layer, wherein each group of memory opening fill structures contacts a respective one of the plurality of source layers; and forming a plurality of source-side select gate electrodes by forming source-side trenches through a first subset of the electrically conductive layers prior to or after formation of the source-level material layer, wherein the source-side trenches do not divide a second subset of the electrically conductive layers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a vertical cross-sectional view of a first exemplary structure after formation of a first vertically alternating sequence of first-tier insulating layers and first-tier sacrificial material layers according to the first embodiment of the present disclosure.

FIG. 1B illustrates a layout of a semiconductor die within the first exemplary structure of FIG. 1A in a plan view.

FIG. 2 is a vertical cross-sectional view of the first exemplary structure after patterning of first stepped surfaces on the first vertically alternating sequence and formation of a first retro-stepped dielectric material portion according to an embodiment of the present disclosure.

FIG. 3A is a vertical cross-sectional view of the first exemplary structure after formation of first-tier memory openings and first-tier support openings according to an embodiment of the present disclosure.

FIG. 3B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 3A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 3A.

FIG. 4 is a vertical cross-sectional view of the first exemplary structure after formation of an optional pedestal channel portion in each of the first-tier memory openings and first-tier support openings according to an embodiment of the present disclosure.

FIG. 5A is a vertical cross-sectional view of the first exemplary structure after formation of first-tier sacrificial memory opening fill structures and first-tier sacrificial support structures according to an embodiment of the present disclosure.

FIG. 5B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 5A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 5A.

FIG. 6 is a vertical cross-sectional view of the first exemplary structure after formation of a second vertically alternating sequence of second-tier insulating layers and second-tier sacrificial material layers, a second-tier retro-stepped dielectric material portion, and a second insulating cap layer according to an embodiment of the present disclosure.

FIG. 7A is a vertical cross-sectional view of the first exemplary structure after formation of second-tier memory openings and second-tier support openings according to an embodiment of the present disclosure.

FIG. 7B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 7A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 7A.

FIG. 7C illustrates horizontal cross-sectional views of various configurations for arrangement of second-tier memory openings according to an embodiment of the present disclosure.

FIG. 8 is a vertical cross-sectional view of the first exemplary structure after formation of inter-tier memory openings and inter-tier support openings according to an embodiment of the present disclosure.

FIGS. 9A-9H are sequential vertical cross-sectional views of an inter-tier memory opening during formation of a memory opening fill structure according to an embodiment of the present disclosure.

FIG. 10A is a vertical cross-sectional view of the first exemplary structure after formation of memory opening fill structures and primary support pillar structures according to an embodiment of the present disclosure.

FIG. 10B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 10A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 10A.

FIG. 11A is a vertical cross-sectional view of the first exemplary structure after formation of backside trenches and source regions according to an embodiment of the present disclosure.

FIG. 11B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 11A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 11A.

FIG. 11C illustrates a layout of the semiconductor die within the first exemplary structure of FIGS. 11A and 11B in a plan view.

FIG. 12A is a vertical cross-sectional view of the first exemplary structure after formation of backside recesses according to an embodiment of the present disclosure.

FIG. 12B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 12A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 12A.

FIG. 13A is a vertical cross-sectional view of the first exemplary structure after replacement of sacrificial material layers with electrically conductive according to an embodiment of the present disclosure.

FIG. 13B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 13A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 13A.

FIG. 14A is a vertical cross-sectional view of the first exemplary structure after formation of backside insulating spacers and backside via structures according to an embodiment of the present disclosure.

FIG. 14B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 14A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 14A.

FIG. 14C illustrates a layout of the semiconductor die within the first exemplary structure of FIGS. 14A and 14B in a plan view.

FIG. 15A is a vertical cross-sectional view of the first exemplary structure after formation of drain contact via cavities and word line contact via cavities according to an embodiment of the present disclosure.

FIG. 15B is a horizontal cross-sectional view of the first exemplary structure along the horizontal plane B-B′ in FIG. 15A. The hinged vertical plane A-A′ corresponds to the plane of the vertical cross-sectional view of FIG. 15A.

FIG. 16A is a vertical cross-sectional view of the first exemplary structure after formation of bit-line-level metal interconnect structures according to an embodiment of the present disclosure.

FIG. 16B is a top-down view of the area of the first exemplary structure of FIG. 16A.

FIGS. 16C and 16D illustrate alternative bit line layouts of a semiconductor die within the first exemplary structure of FIGS. 16A and 16B in a plan view.

FIG. 17A is a vertical cross-sectional view of a logic die according to the first embodiment of the present disclosure.

FIG. 17B illustrates a layout of the logic die of FIG. 17A in a plan view.

FIGS. 18A and 18B are vertical cross-sectional views of the first exemplary structure after bonding the semiconductor die to the logic die according to the first embodiment of the present disclosure.

FIGS. 19A and 19B are vertical cross-sectional views of the first exemplary structure after thinning the backside of the semiconductor die according to the first embodiment of the present disclosure.

FIGS. 20A and 20B are vertical cross-sectional views of the first exemplary structure after formation of a plurality of source layers according to the first embodiment of the present disclosure.

FIG. 21 is a vertical cross-sectional view of a first alternative configuration of the first exemplary structure after formation of a plurality of source layers according to the first embodiment of the present disclosure.

FIGS. 22A-22D are vertical cross-sectional views of an alternative configuration of a memory opening during formation of a memory opening fill structure according to a second embodiment of the present disclosure.

FIG. 23 is a vertical cross-sectional view of a second exemplary structure after removal of the substrate according to a second embodiment of the present disclosure.

FIGS. 24A and 24B are vertical cross-sectional views of a memory opening fill structure during removal of a bottom portion of a memory film according to the second embodiment of the present disclosure.

FIG. 25A is a vertical cross-sectional view of the second exemplary structure after formation of a source-level material layer according to a second embodiment of the present disclosure.

FIG. 25B is a vertical cross-sectional view of a memory opening fill structure within the second exemplary structure of FIG. 25A.

FIGS. 26A and 26B are vertical cross-sectional views of the second exemplary structure after formation of source layers according to a second embodiment of the present disclosure.

FIG. 27 is a circuit schematic of the second exemplary structure of FIGS. 26A and 26B.

FIG. 28 is a vertical cross-sectional view of a third exemplary structure after formation of source-select-level trenches according to a third embodiment of the present disclosure.

FIG. 29 is a vertical cross-sectional view of the third exemplary structure after formation of source-select-level dielectric isolation structures according to the third embodiment of the present disclosure.

FIG. 30 is a vertical cross-sectional view of the third exemplary structure after formation of a source layer according to the third embodiment of the present disclosure.

FIG. 31A is a circuit schematic of the third exemplary structure of FIG. 30 .

FIG. 31B is a schematic top view of the third exemplary structure.

FIG. 32 is a vertical cross-sectional view of a fourth exemplary structure after formation of a source layer according to a fourth embodiment of the present disclosure.

FIG. 33 is a vertical cross-sectional view of the fourth exemplary structure after formation of source-side trenches according to the fourth embodiment of the present disclosure.

FIG. 34 is a vertical cross-sectional view of a first alternative configuration of the fourth exemplary structure after formation of a source-level dielectric isolation layer according to the fourth embodiment of the present disclosure.

FIG. 35 is a vertical cross-sectional view of a second alternative configuration of the fourth exemplary structure after formation of a source-level dielectric isolation layer according to the fourth embodiment of the present disclosure.

FIG. 36 is a circuit schematic of various configurations of the fourth exemplary structure of FIG. 35 .

FIG. 37 is a vertical cross-sectional view of an exemplary structure for providing electrical connections to a source layer according to an embodiment of the present disclosure.

FIG. 38 is a vertical cross-sectional view of another exemplary structure for providing electrical connections to a source layer according to an embodiment of the present disclosure.

FIG. 39A is a vertical cross-sectional view of a fifth exemplary structure after formation of memory opening fill structures according to a fifth embodiment of the present disclosure.

FIG. 39B is a horizontal cross-sectional view of the fifth exemplary structure along the horizontal plane B-B′ of FIG. 39B.

FIG. 40A is a vertical cross-sectional view of the fifth exemplary structure after formation of drain-select-level dielectric isolation structures according to the fifth embodiment of the present disclosure.

FIG. 40B is a horizontal cross-sectional view of the fifth exemplary structure along the horizontal plane B-B′ of FIG. 40A.

FIG. 41 is a vertical cross-sectional view of the fifth exemplary structure after removal of the substrate according to the fifth embodiment of the present disclosure.

FIG. 42 is a vertical cross-sectional view of a region of the fifth exemplary structure of FIG. 41 along the vertical plane A-A′.

FIG. 43 is a vertical cross-sectional view of a region of the fifth exemplary structure after formation of source-select-level trenches according to the fifth embodiment of the present disclosure.

FIG. 44A is a vertical cross-sectional view of a region of the fifth exemplary structure after formation of source-select-level dielectric isolation structures according to the fifth embodiment of the present disclosure.

FIG. 44B is a horizontal cross-sectional view along the horizontal plane B-B′ of the fifth exemplary structure of FIG. 44A.

FIG. 45 is a vertical cross-sectional view of the fifth exemplary structure after formation of a source layer according to the fifth embodiment of the present disclosure.

FIG. 46 is a vertical cross-sectional view of the fifth exemplary structure after dividing the source layer into a plurality of source layers according to the fifth embodiment of the present disclosure.

DETAILED DESCRIPTION

As discussed above, the embodiments of the present disclosure are directed to a three-dimensional memory device containing separated source lines and/or separated source-side select lines, and methods of making the same, the various aspects of which are described herein in detail.

The drawings are not drawn to scale. Multiple instances of an element may be duplicated where a single instance of the element is illustrated, unless absence of duplication of elements is expressly described or clearly indicated otherwise. Ordinals such as “first,” “second,” and “third” are employed merely to identify similar elements, and different ordinals may be employed across the specification and the claims of the instant disclosure. The term “at least one” element refers to all possibilities including the possibility of a single element and the possibility of multiple elements.

The same reference numerals refer to the same element or similar element. Unless otherwise indicated, elements having the same reference numerals are presumed to have the same composition and the same function. Unless otherwise indicated, a “contact” between elements refers to a direct contact between elements that provides an edge or a surface shared by the elements. If two or more elements are not in direct contact with each other or among one another, the two elements are “disjoined from” each other or “disjoined among” one another. As used herein, a first element located “on” a second element can be located on the exterior side of a surface of the second element or on the interior side of the second element. As used herein, a first element is located “directly on” a second element if there exist a physical contact between a surface of the first element and a surface of the second element. As used herein, a first element is “electrically connected to” a second element if there exists a conductive path consisting of at least one conductive material between the first element and the second element. As used herein, a “prototype” structure or an “in-process” structure refers to a transient structure that is subsequently modified in the shape or composition of at least one component therein.

As used herein, a “layer” refers to a material portion including a region having a thickness. A layer may extend over the entirety of an underlying or overlying structure, or may have an extent less than the extent of an underlying or overlying structure. Further, a layer may be a region of a homogeneous or inhomogeneous continuous structure that has a thickness less than the thickness of the continuous structure. For example, a layer may be located between any pair of horizontal planes between, or at, a top surface and a bottom surface of the continuous structure. A layer may extend horizontally, vertically, and/or along a tapered surface. A substrate may be a layer, may include one or more layers therein, or may have one or more layer thereupon, thereabove, and/or therebelow.

As used herein, a first surface and a second surface are “vertically coincident” with each other if the second surface overlies or underlies the first surface and there exists a vertical plane or a substantially vertical plane that includes the first surface and the second surface. A substantially vertical plane is a plane that extends straight along a direction that deviates from a vertical direction by an angle less than 5 degrees. A vertical plane or a substantially vertical plane is straight along a vertical direction or a substantially vertical direction, and may, or may not, include a curvature along a direction that is perpendicular to the vertical direction or the substantially vertical direction.

Generally, a semiconductor package (or a “package”) refers to a unit semiconductor device that can be attached to a circuit board through a set of pins or solder balls. A semiconductor package may include a semiconductor chip (or a “chip”) or a plurality of semiconductor chips that are bonded there amongst, for example, by flip-chip bonding or another chip-to-chip bonding. A package or a chip may include a single semiconductor die (or a “die”) or a plurality of semiconductor dies. A die is the smallest unit that can independently execute external commands or report status. Typically, a package or a chip with multiple dies is capable of simultaneously executing as many number of external commands as the total number of planes therein. Each die includes one or more planes. Identical concurrent operations can be executed in each plane within a same die, although there may be some restrictions. In case a die is a memory die, i.e., a die including memory elements, concurrent read operations, concurrent write operations, or concurrent erase operations can be performed in each plane within a same memory die. In a memory die, each plane contains a number of memory blocks (or “blocks”), which are the smallest unit that can be erased by in a single erase operation. Each memory block contains a number of pages, which are the smallest units that can be selected for programming. A page is also the smallest unit that can be selected to a read operation.

Referring to FIGS. 1A and 1B, a first exemplary structure according to a first embodiment of the present disclosure is illustrated. The first exemplary structure includes a substrate 8 containing a substrate semiconductor layer 9 at least at an upper portion thereof. In one embodiment, the substrate semiconductor layer 9 may be a single crystalline semiconductor material layer or a doped well in a semiconductor substrate, such as a silicon wafer. In another embodiment, the substrate 8 may include a substrate semiconductor layer (not shown) with semiconductor devices (not shown) thereupon, and lower-level dielectric material layers (not shown) embedding lower-level metal interconnect structures (not shown) and located above the semiconductor devices. In this case, the substrate semiconductor layer 9 may be formed over the lower-level dielectric material layers. The substrate semiconductor layer 9 may have a doping of a second conductivity type, which may be p-type or n-type, which is the opposite of a first conductivity type to be employed for doping of vertical semiconductor channels to be subsequently formed. The substrate semiconductor layer 9 may include a single crystalline semiconductor material or a polycrystalline semiconductor material (such as polysilicon or a polycrystalline silicon-germanium alloy).

As used herein, a “semiconducting material” refers to a material having electrical conductivity in the range from 1.0×10⁻⁶ S/cm to 1.0×10⁵ S/cm. As used herein, a “semiconductor material” refers to a material having electrical conductivity in the range from 1.0×10⁻⁶ S/cm to 1.0×10⁵ S/cm in the absence of electrical dopants therein, and is capable of producing a doped material having electrical conductivity in a range from 1.0 S/cm to 1.0×10⁵ S/cm upon suitable doping with an electrical dopant. As used herein, an “electrical dopant” refers to a p-type dopant that adds a hole to a valence band within a band structure, or an n-type dopant that adds an electron to a conduction band within a band structure. As used herein, a “conductive material” refers to a material having electrical conductivity greater than 1.0×10⁵ S/cm. As used herein, an “insulator material” or a “dielectric material” refers to a material having electrical conductivity less than 1.0×10⁻⁶ S/cm. As used herein, a “heavily doped semiconductor material” refers to a semiconductor material that is doped with electrical dopant at a sufficiently high atomic concentration to become a conductive material either as formed as a crystalline material or if converted into a crystalline material through an anneal process (for example, from an initial amorphous state), i.e., to have electrical conductivity greater than 1.0×10⁵ S/cm. A “doped semiconductor material” may be a heavily doped semiconductor material, or may be a semiconductor material that includes electrical dopants (i.e., p-type dopants and/or n-type dopants) at a concentration that provides electrical conductivity in the range from 1.0×10⁻⁶ S/cm to 1.0×10⁵ S/cm. An “intrinsic semiconductor material” refers to a semiconductor material that is not doped with electrical dopants. Thus, a semiconductor material may be semiconducting or conductive, and may be an intrinsic semiconductor material or a doped semiconductor material. A doped semiconductor material can be semiconducting or conductive depending on the atomic concentration of electrical dopants therein. As used herein, a “metallic material” refers to a conductive material including at least one metallic element therein. All measurements for electrical conductivities are made at the standard condition.

A vertically alternating sequence of first material layers and second material layers is subsequently formed. Each first material layer can include a first material, and each second material layer can include a second material that is different from the first material. In case at least another vertically alternating sequence of material layers is subsequently formed over the vertically alternating sequence of the first material layers and the second material layers, the vertically alternating sequence is herein referred to as a first vertically alternating sequence. The level of the first vertically alternating sequence is herein referred to as a first-tier level, and the level of the vertically alternating sequence to be subsequently formed immediately above the first-tier level is herein referred to as a second-tier level, etc.

The first vertically alternating sequence can include first-tier insulating layers 132 as the first material layers, and first-tier sacrificial material layers 142 as the second material layers. In one embodiment, each first-tier insulating layer 132 can include a first insulating material, and each first-tier sacrificial material layer 142 can include a first sacrificial material. An alternating plurality of first-tier insulating layers 132 and first-tier sacrificial material layers 142 is formed over the substrate semiconductor layer 9. As used herein, a “sacrificial material” refers to a material that is removed during a subsequent processing step.

The first vertically alternating sequence (132, 142) can include first-tier insulating layers 132 composed of the first material, and first-tier sacrificial material layers 142 composed of the second material, which is different from the first material. The first material of the first-tier insulating layers 132 can be at least one insulating material. Insulating materials that can be employed for the first-tier insulating layers 132 include, but are not limited to silicon oxide (including doped or undoped silicate glass), silicon nitride, silicon oxynitride, organosilicate glass (OSG), spin-on dielectric materials, dielectric metal oxides that are commonly known as high dielectric constant (high-k) dielectric oxides (e.g., aluminum oxide, hafnium oxide, etc.) and silicates thereof, dielectric metal oxynitrides and silicates thereof, and organic insulating materials. In one embodiment, the first material of the first-tier insulating layers 132 can be silicon oxide.

The second material of the first-tier sacrificial material layers 142 is a sacrificial material that can be removed selective to the first material of the first-tier insulating layers 132. As used herein, a removal of a first material is “selective to” a second material if the removal process removes the first material at a rate that is at least twice the rate of removal of the second material. The ratio of the rate of removal of the first material to the rate of removal of the second material is herein referred to as a “selectivity” of the removal process for the first material with respect to the second material.

The first-tier sacrificial material layers 142 may comprise an insulating material, a semiconductor material, or a conductive material. The second material of the first-tier sacrificial material layers 142 can be subsequently replaced with electrically conductive electrodes which can function, for example, as control gate electrodes of a vertical NAND device. In one embodiment, the first-tier sacrificial material layers 142 can be material layers that comprise silicon nitride.

In one embodiment, the first-tier insulating layers 132 can include silicon oxide, and sacrificial material layers can include silicon nitride sacrificial material layers. The first material of the first-tier insulating layers 132 can be deposited, for example, by chemical vapor deposition (CVD). For example, if silicon oxide is employed for the first-tier insulating layers 132, tetraethylorthosilicate (TEOS) can be employed as the precursor material for the CVD process. The second material of the first-tier sacrificial material layers 142 can be formed, for example, CVD or atomic layer deposition (ALD).

The thicknesses of the first-tier insulating layers 132 and the first-tier sacrificial material layers 142 can be in a range from 20 nm to 50 nm, although lesser and greater thicknesses can be employed for each first-tier insulating layer 132 and for each first-tier sacrificial material layer 142. The number of repetitions of the pairs of a first-tier insulating layer 132 and a first-tier sacrificial material layer 142 can be in a range from 2 to 1,024, and typically from 8 to 256, although a greater number of repetitions can also be employed. In one embodiment, each first-tier sacrificial material layer 142 in the first vertically alternating sequence (132, 142) can have a uniform thickness that is substantially invariant within each respective first-tier sacrificial material layer 142. Each layer within the first vertically alternating sequence (132, 142) can be a continuous material layer without any opening therethrough. As such, the first vertically alternating sequence (132, 142) can include a vertically alternating sequence of continuous insulating layers and continuous sacrificial material layers.

A first insulating cap layer 170 is subsequently formed over the stack (132, 142). The first insulating cap layer 170 includes a dielectric material, which can be any dielectric material that can be employed for the first-tier insulating layers 132. In one embodiment, the first insulating cap layer 170 includes the same dielectric material as the first-tier insulating layers 132. The thickness of the first insulating cap layer 170 can be in a range from 20 nm to 300 nm, although lesser and greater thicknesses can also be employed.

Generally, the substrate semiconductor layer 9 and the material layers thereupon can be employed to form a memory die. The memory die may include a plurality of planes (P0-P7). The exemplary layout illustrated in FIG. 1B includes eight planes (P0-P7), which can be independently operated within a memory die. Each plane (P0-P7) can include a respective three-dimensional memory array containing plural blocks upon completion of the memory die. Each plane (P0-P7) can include a respective memory array region 100, a respective contact region 200, and a respective peripheral region 300. A gap region G can be provided between neighboring pairs of planes (P0-P7). In one embodiment, the gap region G can laterally extend along a first horizontal direction (i.e., word line direction) hd1, and neighboring pairs of planes (P0 and P1; P2 and P3; P4 and P5; P6 and P7) that neighbor along the second horizontal direction (e.g., bit line direction) hd2 can be laterally spaced apart by the gap region G along a second horizontal direction hd2 that is perpendicular to the first horizontal direction hd1. According to an aspect of the present disclosure, the width of each gap region G can be the same as the width of a respective backside trench to be subsequently formed between adjacent blocks in the same memory plane. In an illustrative example, the width of each gap region G may be in a range from 300 nm to 3,000 nm, although lesser and greater widths may also be employed. Neighboring pairs of planes (P0 and P2; P4 and P6; P1 and P3; P5 and P7) that neighbor along the first horizontal direction hd1 can be laterally spaced apart by the respective contact region 200.

Referring to FIG. 2 , the first insulating cap layer 170 and the first vertically alternating sequence (132, 142) can be patterned to form first stepped surfaces in the contact region 200. The contact region 200 can include a respective first stepped area in which the first stepped surfaces are formed, and a second stepped area in which additional stepped surfaces are to be subsequently formed in a second-tier structure (to be subsequently formed over a first-tier structure) and/or additional tier structures. The first stepped surfaces can be formed, for example, by forming a mask layer with an opening therein, etching a cavity within the levels of the first insulating cap layer 170, and iteratively expanding the etched area and vertically recessing the cavity by etching each pair of a first-tier insulating layer 132 and a first-tier sacrificial material layer 142 located directly underneath the bottom surface of the etched cavity within the etched area. The first stepped surfaces continuously extend from a bottommost layer within the first vertically alternating sequence (132, 142) to a topmost layer within the first vertically alternating sequence (132, 142). The cavity overlying the first stepped surfaces is herein referred to as a first stepped cavity.

A dielectric material, such as a silicate glass, can be deposited in the first stepped cavity. The dielectric material is subsequently planarized to provide a planar surface within a horizontal plane including a top surface of the first insulating cap layer. A continuous remaining portion of the dielectric material overlying the first stepped surfaces and filling the first stepped cavity is herein referred to as a first retro-stepped dielectric material portion 165, which comprises, and can consist of, the first silicate glass material. As used herein, a “retro-stepped” element refers to an element that has stepped surfaces and a horizontal cross-sectional area that increases monotonically as a function of a vertical distance from a top surface of a substrate on which the element is present. The first vertically alternating sequence (132, 142) and the first retro-stepped dielectric material portion 165 collectively constitute a first-tier structure, which is an in-process structure that is subsequently modified.

An inter-tier dielectric layer 180 may be optionally deposited over the first-tier structure (132, 142, 165, 170). The inter-tier dielectric layer 180 includes a dielectric material such as a silicate glass material. The thickness of the inter-tier dielectric layer 180 can be in a range from 30 nm to 300 nm, although lesser and greater thicknesses can also be employed. In one embodiment, the inter-tier dielectric layer 180 can include a silicate glass that provides a greater etch rate in hydrofluoric acid than undoped silicate glass. For example, the inter-tier dielectric layer 180 can include borosilicate glass.

The combination of all material portions formed over the top surface of the substrate semiconductor layer 9 and underneath the inter-tier dielectric layer 180 constitutes a first-tier structure (132, 142, 165). The first-tier structure (132, 142, 165) comprises a first vertically alternating sequence of first-tier insulating layers 132 and first-tier sacrificial material layers 142 and a first retro-stepped dielectric material portion 165 overlying, and contacting, first stepped surfaces of the first vertically alternating sequence (132, 142). The first stepped surfaces continuously extend from a bottommost layer within the first vertically alternating sequence (132, 142) to a topmost layer within the first vertically alternating sequence (132, 142) and contacts vertical surfaces and horizontal bottom surfaces of the first retro-stepped dielectric material portion 165.

Referring to FIGS. 3A and 3B, first-tier memory openings 149 and first-tier support openings 119 can be formed. Locations of steps S in the first vertically alternating sequence (132, 142) are illustrated as dotted lines in FIG. 3B. The first-tier memory openings 149 and the first-tier support openings 119 extend through the first vertically alternating sequence (132, 142) at least to a top surface of the substrate semiconductor layer 9. The first-tier memory openings 149 can be formed in the memory array region 100 at locations at which memory stack structures including vertical stacks of memory elements are to be subsequently formed. The first-tier support openings 119 can be formed in the contact region 200. The first-tier support openings 119 can be formed within a first area of the first stepped surfaces at which the first retro-stepped dielectric material portion 165 contacts the first vertically alternating sequence (132, 142) and within a second area of the contact region 200 in which second stepped surfaces of a second vertically alternating sequence are to be subsequently formed. The second area of the contact region 200 is located between the first area of the word line contact region and the memory array region 100.

For example, a lithographic material stack (not shown) including at least a photoresist layer can be formed over the first insulating cap layer 170 (and the optional inter-tier dielectric layer 180, if present), and can be lithographically patterned to form openings within the lithographic material stack. The pattern in the lithographic material stack can be transferred through the first insulating cap layer 170 (and the optional inter-tier dielectric layer 180), and through the entirety of the first vertically alternating sequence (132, 142) by at least one anisotropic etch that employs the patterned lithographic material stack as an etch mask. Portions of the first insulating cap layer 170 (and the optional inter-tier dielectric layer 180), and the first vertically alternating sequence (132, 142) underlying the openings in the patterned lithographic material stack are etched to form the first-tier memory openings 149 and the first-tier support openings 119. In other words, the transfer of the pattern in the patterned lithographic material stack through the first insulating cap layer 170 and the first vertically alternating sequence (132, 142) forms the first-tier memory openings 149 and the first-tier support openings 119.

In one embodiment, the chemistry of the anisotropic etch process employed to etch through the materials of the first vertically alternating sequence (132, 142) can alternate to optimize etching of the first and second materials in the first vertically alternating sequence (132, 142). The anisotropic etch can be, for example, a series of reactive ion etches or a single etch (e.g., CF₄/O₂/Ar etch). The sidewalls of the first-tier memory openings 149 and the support openings 119. Subsequently, the patterned lithographic material stack can be subsequently removed, for example, by ashing.

Generally, groups of first-tier memory openings 149 can be formed through the first vertically alternating sequence (132, 142). Each group of first-tier memory openings 149 can be formed within a rectangular area (e.g., area of a memory block) that laterally extends along a first horizontal direction (e.g., word line direction) hd1. Each group of first-tier memory openings 149 can include a plurality of rows of first-tier memory openings 149. Each row of first-tier memory openings 149 can laterally extend along the first horizontal direction hd1. Rows of first-tier memory openings 149 can be laterally spaced apart from each other along the second horizontal direction (e.g., bit line direction) hd2.

Optionally, the portions of the first-tier memory openings 149 and the first-tier support openings 119 at the level of the inter-tier dielectric layer 180 can be laterally expanded by an isotropic etch. For example, if the inter-tier dielectric layer 180 comprises a dielectric material (such as borosilicate glass) having a greater etch rate than the first-tier insulating layers 132 (that can include undoped silicate glass), an isotropic etch (such as a wet etch employing HF) can be employed to expand the lateral dimensions of the first-tier memory openings at the level of the inter-tier dielectric layer 180.

Referring to FIG. 4 , pedestal channel portions 11 may be optionally formed at the bottom of each of the first-tier memory openings 149 and the first-tier support openings 119. The pedestal channel portions 11 may be formed by a selective semiconductor deposition process that deposits a doped semiconductor material having a doping of a first conductivity type. If the pedestal channel portions 11 are formed, top surfaces of the pedestal channel portions 11 can be formed at, or above, the horizontal plane including the top surface of the bottommost first-tier sacrificial material layer 142 and the horizontal plane including the bottom surface of the first-tier sacrificial material layer 42 that is most proximal to the bottommost first-tier sacrificial material layer 142 (i.e., the second-from-the-bottom second-tier sacrificial material layer 142).

Referring to FIGS. 5A and 5B, first-tier sacrificial memory opening fill structures 148 can be formed in the first-tier memory openings 149, and first-tier sacrificial support structures 118 can be formed in the first-tier support openings 119. For example, a fill material layer including a fill material is deposited in the first-tier memory openings 149 and the first-tier support openings 119.

Referring to FIG. 6 , a second-tier structure can be formed over the first-tier structure (132, 142, 170, 148, 118). The second-tier structure can include an additional vertically alternating sequence of insulating layers and sacrificial material layers, which can be sacrificial material layers. For example, a second vertically alternating sequence (232, 242) of material layers can be subsequently formed on the top surface of the first vertically alternating sequence (132, 142). The second stack (232, 242) includes an alternating plurality of third material layers and fourth material layers. Each third material layer can include a third material, and each fourth material layer can include a fourth material that is different from the third material. In one embodiment, the third material can be the same as the first material of the first-tier insulating layer 132, and the fourth material can be the same as the second material of the first-tier sacrificial material layers 142.

In one embodiment, the third material layers can be second-tier insulating layers 232 and the fourth material layers can be second-tier sacrificial material layers 242 that provide vertical spacing between each vertically neighboring pair of the second-tier insulating layers 232. In one embodiment, the third material layers and the fourth material layers can be second-tier insulating layers 232 and second-tier sacrificial material layers 242, respectively.

The third material of the second-tier insulating layers 232 may be at least one insulating material. The fourth material of the second-tier sacrificial material layers 242 may be a sacrificial material that can be removed selective to the third material of the second-tier insulating layers 232. The second-tier sacrificial material layers 242 may comprise an insulating material, a semiconductor material, or a conductive material. The fourth material of the second-tier sacrificial material layers 242 can be subsequently replaced with electrically conductive electrodes which can function, for example, as control gate electrodes of a vertical NAND device.

In one embodiment, each second-tier insulating layer 232 can include a second insulating material, and each second-tier sacrificial material layer 242 can include a second sacrificial material. In this case, the second stack (232, 242) can include an alternating plurality of second-tier insulating layers 232 and second-tier sacrificial material layers 242. The third material of the second-tier insulating layers 232 can be deposited, for example, by chemical vapor deposition (CVD). The fourth material of the second-tier sacrificial material layers 242 can be formed, for example, CVD or atomic layer deposition (ALD).

The third material of the second-tier insulating layers 232 can be at least one insulating material. Insulating materials that can be employed for the second-tier insulating layers 232 can be any material that can be employed for the first-tier insulating layers 132. The fourth material of the second-tier sacrificial material layers 242 is a sacrificial material that can be removed selective to the third material of the second-tier insulating layers 232. Sacrificial materials that can be employed for the second-tier sacrificial material layers 242 can be any material that can be employed for the first-tier sacrificial material layers 142. In one embodiment, the second insulating material can be the same as the first insulating material, and the second sacrificial material can be the same as the first sacrificial material.

The thicknesses of the second-tier insulating layers 232 and the second-tier sacrificial material layers 242 can be in a range from 20 nm to 50 nm, although lesser and greater thicknesses can be employed for each second-tier insulating layer 232 and for each second-tier sacrificial material layer 242. The number of repetitions of the pairs of a second-tier insulating layer 232 and a second-tier sacrificial material layer 242 can be in a range from 2 to 1,024, and typically from 8 to 256, although a greater number of repetitions can also be employed. In one embodiment, each second-tier sacrificial material layer 242 in the second stack (232, 242) can have a uniform thickness that is substantially invariant within each respective second-tier sacrificial material layer 242.

The second vertically alternating sequence (232, 242) can be patterned to form second stepped surfaces in the second stepped area within the contact region 200. The second stepped area is more proximal to the memory array region 100 than the first stepped area including the first stepped surfaces is to the memory array region. The second stepped surfaces can be formed, for example, by forming a mask layer with an opening therein, etching a cavity within a topmost second-tier sacrificial material layer 242 and a topmost second-tier insulating layer 232, and iteratively expanding the etched area and vertically recessing the cavity by etching each pair of a first-tier insulating layer 132 and a first-tier sacrificial material layer 142 located directly underneath the bottom surface of the etched cavity within the etched area. The second stepped surfaces continuously extend from a bottommost layer within the second vertically alternating sequence (232, 242) to a topmost layer within the first vertically alternating sequence (132, 142). The cavity overlying the second stepped surfaces is herein referred to as a first stepped cavity.

A dielectric material such as silicon oxide can be deposited over the second stepped surfaces. Portions of the dielectric material that overlie the second vertically alternating sequence (232, 242) can be removed by a planarization process such as a chemical mechanical planarization (CMP) process. A continuous remaining portion of the dielectric material overlying the second stepped surfaces and filling the second stepped cavity is herein referred to as a second retro-stepped dielectric material portion 265. The second vertically alternating sequence (232, 242) and the second retro-stepped dielectric material portion 265 collectively constitute a second-tier structure, which is an in-process structure that is subsequently modified. The second stepped surfaces continuously extend from a bottommost layer within the second vertically alternating sequence (232, 242) to a topmost layer within the second vertically alternating sequence (232, 242) and contacts vertical surfaces and horizontal bottom surfaces of the second retro-stepped dielectric material portion 265.

A second insulating cap layer 270 can be subsequently formed over the second vertically alternating sequence (232, 242). The second insulating cap layer 270 includes a dielectric material that is different from the material of the second-tier sacrificial material layers 242. In one embodiment, the second insulating cap layer 270 can include silicon oxide.

Optionally, drain-select-level dielectric isolation structures 72 can be formed through a subset of layers in an upper portion of the second vertically alternating sequence (232, 242). The second-tier sacrificial material layers 242 that are cut by the drain-select-level dielectric isolation structures 72 correspond to the levels in which drain-select-level electrically conductive layers are subsequently formed. The drain-select-level dielectric isolation structures 72 include a dielectric material such as silicon oxide.

Generally, a subset of the spacer material layers (such as a distal subset of the second-tier sacrificial material layers 246 that is most distal from the substrate including the substrate semiconductor layer 9) can be divided by forming drain-select-level trenches after formation of the groups of memory opening fill structures 58. The drain-select-level dielectric isolation structures 72 can be formed by depositing the dielectric material in the drain-select-level trenches. The drain-select-level dielectric isolation structures 72 can laterally extend along the first horizontal direction hd1.

Referring to FIGS. 7A-7C, second-tier memory openings 249 and second tier support openings 219 extending through the second-tier structure (232, 242, 270, 265) are formed in areas overlying the sacrificial memory opening fill portions 148. A photoresist layer can be applied over the second-tier structure (232, 242, 270, 265), and can be lithographically patterned to form a same pattern as the pattern of the sacrificial memory opening fill portions 148 and the first-tier sacrificial support structures 118, i.e., the pattern of the first-tier memory openings 149 and the first-tier support openings 119. An anisotropic etch can be performed to transfer the pattern of the lithographically patterned photoresist layer through the second-tier structure (232, 242, 270, 265). In one embodiment, the chemistry of the anisotropic etch process employed to etch through the materials of the second vertically alternating sequence (232, 242) can alternate to optimize etching of the alternating material layers in the second vertically alternating sequence (232, 242). The anisotropic etch can be, for example, a series of reactive ion etches. The patterned lithographic material stack can be removed, for example, by ashing after the anisotropic etch process.

A top surface of an underlying sacrificial memory opening fill portion 148 can be physically exposed at the bottom of each second-tier memory opening 249. A top surface of an underlying first-tier sacrificial support structure 118 can be physically exposed at the bottom of each second-tier support opening 219.

Generally, groups of second-tier memory openings 249 can be formed through the second vertically alternating sequence (232, 242). Each group of second-tier memory openings 249 can be formed within a rectangular area (e.g., memory block area) that laterally extends along the first horizontal direction hd1. Each group of second-tier memory openings 249 can include a plurality of rows of second-tier memory openings 249. Each row of second-tier memory openings 249 can laterally extend along the first horizontal direction hd1. Rows of second-tier memory openings 249 can be laterally spaced apart from each other along the second horizontal direction (e.g., bit line direction) hd2. The number of rows within each group of second tier-memory openings 249 (e.g., in a memory string unit) depends on the total number of drain-select-level dielectric isolation structures 72 per group of second-tier memory openings 249. In one embodiment, the drain-select-level dielectric isolation structures 72 are formed such that the area of each drain-select-level dielectric isolation structure 72 overlaps with a row of second-tier memory openings 249. FIG. 7C illustrates examples in which the total number of rows of drain-select-level dielectric isolation structures 72 within each memory block (i.e., within each group of second-tier memory openings 249) is 1, 4 or 7, which results in memory blocks having 8, 20 or 32 staggered rows, respectively, of second-tier memory openings 249. In these memory blocks, there will be 2, 5 or 8 drain-side select lines, respectively, formed in a drain-select line level, which results in 2, 5 or 8 memory string units, respectively in each memory block. As can be seen in FIG. 7C, the memory block size increases with the increased number of staggered rows of second-tier memory openings 249.

Referring to FIG. 8 , an etch process can be performed after the top surfaces of the sacrificial memory opening fill portions 148 and the first-tier sacrificial support structures 118 are physically exposed. The etch process removes the sacrificial material of the sacrificial memory opening fill portions 148 and the first-tier sacrificial support structures 118 selective to the materials of the second vertically alternating sequence (232, 242) and the first vertically alternating sequence (132, 142) (e.g., C₄F₈/O₂/Ar etch). The etch process may include an anisotropic etch process or an isotropic etch process.

Upon removal of the sacrificial memory opening fill portions 148, each vertically adjoining pair of a second-tier memory opening 249 and a first-tier memory opening 149 forms a continuous cavity that extends through the first vertically alternating sequence (132, 142) and the second vertically alternating sequence (232, 242), which is herein referred to as an inter-tier memory opening 49, or a memory opening 49. Likewise, upon removal of the first-tier sacrificial support structures 118, each vertically adjoining pair of a second-tier support opening 219 and a first-tier support opening 119 forms a continuous cavity that extends through the first vertically alternating sequence (132, 142) and the second vertically alternating sequence (232, 242), which is herein referred to as an inter-tier support opening 19, or a support opening 19. A top surface of the substrate semiconductor layer 9 can be physically exposed at the bottom of each memory opening and at the bottom of each support openings. Locations of steps S in the first vertically alternating sequence (132, 142) and the second vertically alternating sequence (232, 242) are illustrated as dotted lines.

Generally, at least one vertically alternating sequence of continuous insulating layers and continuous sacrificial material layers can be formed over a substrate. Memory openings 49 are formed through the at least one vertical alternating sequence.

FIGS. 9A-9H provide sequential cross-sectional views of a memory opening 49 or a support opening 19 during formation of a memory opening fill structure 58 or a primary support pillar structure 20. While a structural change in a memory opening 49 is illustrated in FIGS. 9A-9H, it is understood that the same structural change occurs in each memory openings 49 and in each of the support openings 19 during the same set of processing steps.

Referring to FIG. 9A, a memory opening 49 in the exemplary device structure of FIG. 14 is illustrated. The memory opening 49 extends through the first-tier structure and the second-tier structure. Likewise, each support opening 19 extends through the first-tier structure and the second-tier structure. A pedestal channel portion 11 may, or may not, be present within each memory opening 49 and within each support opening 19. A cavity 49′ is present in the unfilled portion of the memory opening 49 (or of the support opening) above the pedestal channel portion 11.

Referring to FIG. 9B, a stack of layers including a blocking dielectric layer 52, a charge storage layer 54, and a tunneling dielectric layer 56 can be sequentially deposited in the memory openings 49. The blocking dielectric layer 52 can include a single dielectric material layer or a stack of a plurality of dielectric material layers. In one embodiment, the blocking dielectric layer can include a dielectric metal oxide layer consisting essentially of a dielectric metal oxide. As used herein, a dielectric metal oxide refers to a dielectric material that includes at least one metallic element and at least oxygen. The dielectric metal oxide may consist essentially of the at least one metallic element and oxygen, or may consist essentially of the at least one metallic element, oxygen, and at least one non-metallic element such as nitrogen.

In one embodiment, the blocking dielectric layer 52 can include a dielectric metal oxide having a dielectric constant greater than 7.9, i.e., having a dielectric constant greater than the dielectric constant of silicon nitride. Non-limiting examples of dielectric metal oxides include aluminum oxide (Al₂O₃), hafnium oxide (HfO₂), lanthanum oxide (LaO₂), yttrium oxide (Y₂O₃), tantalum oxide (Ta₂O₅), silicates thereof, nitrogen-doped compounds thereof, alloys thereof, and stacks thereof.

The dielectric metal oxide layer can be deposited, for example, by chemical vapor deposition (CVD), atomic layer deposition (ALD), pulsed laser deposition (PLD), liquid source misted chemical deposition, or a combination thereof. The thickness of the dielectric metal oxide layer can be in a range from 1 nm to 20 nm, although lesser and greater thicknesses can also be employed. The dielectric metal oxide layer can subsequently function as a dielectric material portion that blocks leakage of stored electrical charges to control gate electrodes. In one embodiment, the blocking dielectric layer 52 includes aluminum oxide. In one embodiment, the blocking dielectric layer 52 can include multiple dielectric metal oxide layers having different material compositions.

Alternatively or additionally, the blocking dielectric layer 52 can include a dielectric silicon compound, such as silicon oxide, silicon oxynitride, silicon nitride, or a combination thereof. In one embodiment, the blocking dielectric layer 52 can include silicon oxide. In this case, the dielectric semiconductor compound of the blocking dielectric layer 52 can be formed by a conformal deposition method such as low pressure chemical vapor deposition, atomic layer deposition, or a combination thereof.

The thickness of the dielectric semiconductor compound can be in a range from 1 nm to 20 nm, although lesser and greater thicknesses can also be employed. Alternatively, the blocking dielectric layer 52 can be omitted, and a backside blocking dielectric layer can be formed after formation of backside recesses on surfaces of memory films to be subsequently formed.

Subsequently, the charge storage layer 54 can be formed. In one embodiment, the charge storage layer 54 can be a continuous layer or patterned discrete portions of a charge trapping material including a dielectric charge trapping material, which can be, for example, silicon nitride. Alternatively, the charge storage layer 54 can include a continuous layer or patterned discrete portions of a conductive material such as doped polysilicon or a metallic material that is patterned into multiple electrically isolated portions (e.g., floating gates), for example, by being formed within lateral recesses into sacrificial material layers (142, 242). In one embodiment, the charge storage layer 54 includes a silicon nitride layer. In one embodiment, the sacrificial material layers (142, 242) and the insulating layers (132, 232) can have vertically coincident sidewalls, and the charge storage layer 54 can be formed as a single continuous layer.

In another embodiment, the sacrificial material layers (142, 242) can be laterally recessed with respect to the sidewalls of the insulating layers (132, 232), and a combination of a deposition process and an anisotropic etch process can be employed to form the charge storage layer 54 as a plurality of memory material portions that are vertically spaced apart. While the present disclosure is described employing an embodiment in which the charge storage layer 54 is a single continuous layer, embodiments are expressly contemplated herein in which the charge storage layer 54 is replaced with a plurality of memory material portions (which can be charge trapping material portions or electrically isolated conductive material portions) that are vertically spaced apart.

The charge storage layer 54 can be formed as a single charge storage layer of homogeneous composition, or can include a stack of multiple charge storage layers. The multiple charge storage layers, if employed, can comprise a plurality of spaced-apart floating gate material layers that contain conductive materials (e.g., metal such as tungsten, molybdenum, tantalum, titanium, platinum, ruthenium, and alloys thereof, or a metal silicide such as tungsten silicide, molybdenum silicide, tantalum silicide, titanium silicide, nickel silicide, cobalt silicide, or a combination thereof) and/or semiconductor materials (e.g., polycrystalline or amorphous semiconductor material including at least one elemental semiconductor element or at least one compound semiconductor material). Alternatively or additionally, the charge storage layer 54 may comprise an insulating charge trapping material, such as one or more silicon nitride segments. Alternatively, the charge storage layer 54 may comprise conductive nanoparticles such as metal nanoparticles, which can be, for example, ruthenium nanoparticles. The charge storage layer 54 can be formed, for example, by chemical vapor deposition (CVD), atomic layer deposition (ALD), physical vapor deposition (PVD), or any suitable deposition technique for storing electrical charges therein. The thickness of the charge storage layer 54 can be in a range from 2 nm to 20 nm, although lesser and greater thicknesses can also be employed.

The tunneling dielectric layer 56 includes a dielectric material through which charge tunneling can be performed under suitable electrical bias conditions. The charge tunneling may be performed through hot-carrier injection or by Fowler-Nordheim tunneling induced charge transfer depending on the mode of operation of the monolithic three-dimensional NAND string memory device to be formed. The tunneling dielectric layer 56 can include silicon oxide, silicon nitride, silicon oxynitride, dielectric metal oxides (such as aluminum oxide and hafnium oxide), dielectric metal oxynitride, dielectric metal silicates, alloys thereof, and/or combinations thereof. In one embodiment, the tunneling dielectric layer 56 can include a stack of a first silicon oxide layer, a silicon oxynitride layer, and a second silicon oxide layer, which is commonly known as an ONO stack. In one embodiment, the tunneling dielectric layer 56 can include a silicon oxide layer that is substantially free of carbon or a silicon oxynitride layer that is substantially free of carbon. The thickness of the tunneling dielectric layer 56 can be in a range from 2 nm to 20 nm, although lesser and greater thicknesses can also be employed.

Referring to FIG. 9C, an optional first semiconductor channel layer 601 can be deposited by a conformal deposition process. The optional first semiconductor channel layer 601 includes a semiconductor material such as at least one elemental semiconductor material, at least one III-V compound semiconductor material, at least one II-VI compound semiconductor material, at least one organic semiconductor material, or other semiconductor materials known in the art. In one embodiment, the first semiconductor channel layer 601 includes amorphous silicon or polysilicon. The first semiconductor channel layer 601 can be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the first semiconductor channel layer 601 can be in a range from 2 nm to 10 nm, although lesser and greater thicknesses can also be employed. A cavity 49′ is formed in the volume of each memory opening 49 that is not filled with the deposited material layers (52, 54, 56, 601).

Referring to FIG. 9D, the optional first semiconductor channel layer 601, the tunneling dielectric layer 56, the charge storage layer 54, the blocking dielectric layer 52 are sequentially anisotropically etched employing at least one anisotropic etch process. The portions of the first semiconductor channel layer 601, the tunneling dielectric layer 56, the charge storage layer 54, and the blocking dielectric layer 52 located above the top surface of the second insulating cap layer 270 can be removed by the at least one anisotropic etch process. Further, the horizontal portions of the first semiconductor channel layer 601, the tunneling dielectric layer 56, the charge storage layer 54, and the blocking dielectric layer 52 at a bottom of each cavity 49′ can be removed to form openings in remaining portions thereof. Each of the first semiconductor channel layer 601, the tunneling dielectric layer 56, the charge storage layer 54, and the blocking dielectric layer 52 can be etched by a respective anisotropic etch process employing a respective etch chemistry, which may, or may not, be the same for the various material layers.

Each remaining portion of the first semiconductor channel layer 601 can have a tubular configuration. The charge storage layer 54 can comprise a charge trapping material or a floating gate material. In one embodiment, each charge storage layer 54 can include a vertical stack of charge storage regions that store electrical charges upon programming. In one embodiment, the charge storage layer 54 can be a charge storage layer in which each portion adjacent to the sacrificial material layers (142, 242) constitutes a charge storage region.

A surface of the pedestal channel portion 11 (or a surface of the substrate semiconductor layer 9 in case the pedestal channel portions 11 are not employed) can be physically exposed underneath the opening through the first semiconductor channel layer 601, the tunneling dielectric layer 56, the charge storage layer 54, and the blocking dielectric layer 52. Optionally, the physically exposed semiconductor surface at the bottom of each cavity 49′ can be vertically recessed so that the recessed semiconductor surface underneath the cavity 49′ is vertically offset from the topmost surface of the pedestal channel portion 11 (or of the semiconductor material layer 10 in case pedestal channel portions 11 are not employed) by a recess distance. A tunneling dielectric layer 56 is located over the charge storage layer 54. A set of a blocking dielectric layer 52, a charge storage layer 54, and a tunneling dielectric layer 56 in a memory opening 49 constitutes a memory film 50, which includes a plurality of charge storage regions (as embodied as the charge storage layer 54) that are insulated from surrounding materials by the blocking dielectric layer 52 and the tunneling dielectric layer 56. In one embodiment, the first semiconductor channel layer 601, the tunneling dielectric layer 56, the charge storage layer 54, and the blocking dielectric layer 52 can have vertically coincident sidewalls.

Referring to FIG. 9E, a second semiconductor channel layer 602 can be deposited directly on the semiconductor surface of the pedestal channel portion 11 or the semiconductor material layer 10 if the pedestal channel portion 11 is omitted, and directly on the first semiconductor channel layer 601. The second semiconductor channel layer 602 includes a semiconductor material such as at least one elemental semiconductor material, at least one III-V compound semiconductor material, at least one II-VI compound semiconductor material, at least one organic semiconductor material, or other semiconductor materials known in the art. In one embodiment, the second semiconductor channel layer 602 includes amorphous silicon or polysilicon. The second semiconductor channel layer 602 can be formed by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD). The thickness of the second semiconductor channel layer 602 can be in a range from 2 nm to 10 nm, although lesser and greater thicknesses can also be employed. The second semiconductor channel layer 602 may partially fill the cavity 49′ in each memory opening, or may fully fill the cavity in each memory opening.

The materials of the first semiconductor channel layer 601 and the second semiconductor channel layer 602 are collectively referred to as a semiconductor channel material. In other words, the semiconductor channel material is a set of all semiconductor material in the first semiconductor channel layer 601 and the second semiconductor channel layer 602.

Referring to FIG. 9F, in case the cavity 49′ in each memory opening is not completely filled by the second semiconductor channel layer 602, a dielectric core layer 62L can be deposited in the cavity 49′ to fill any remaining portion of the cavity 49′ within each memory opening. The dielectric core layer 62L includes a dielectric material such as silicon oxide or organosilicate glass. The dielectric core layer 62L can be deposited by a conformal deposition method such as low pressure chemical vapor deposition (LPCVD), or by a self-planarizing deposition process such as spin coating.

Referring to FIG. 9G, the horizontal portion of the dielectric core layer 62L can be removed, for example, by a recess etch from above the top surface of the second insulating cap layer 270. Each remaining portion of the dielectric core layer 62L constitutes a dielectric core 62. Further, the horizontal portion of the second semiconductor channel layer 602 located above the top surface of the second insulating cap layer 270 can be removed by a planarization process, which can employ a recess etch or chemical mechanical planarization (CMP). Each remaining portion of the second semiconductor channel layer 602 can be located entirety within a memory opening 49 or entirely within a support opening 19.

Each adjoining pair of a first semiconductor channel layer 601 and a second semiconductor channel layer 602 can collectively form a vertical semiconductor channel 60 through which electrical current can flow when a vertical NAND device including the vertical semiconductor channel 60 is turned on. A tunneling dielectric layer 56 is surrounded by a charge storage layer 54, and laterally surrounds a portion of the vertical semiconductor channel 60. Each adjoining set of a blocking dielectric layer 52, a charge storage layer 54, and a tunneling dielectric layer 56 collectively constitute a memory film 50, which can store electrical charges with a macroscopic retention time. In some embodiments, a blocking dielectric layer 52 may not be present in the memory film 50 at this step, and a blocking dielectric layer may be subsequently formed after formation of backside recesses. As used herein, a macroscopic retention time refers to a retention time suitable for operation of a memory device as a permanent memory device such as a retention time in excess of 24 hours.

Referring to FIG. 9H, the top surface of each dielectric core 62 can be further recessed within each memory opening, for example, by a recess etch to a depth that is located between the top surface of the second insulating cap layer 270 and the bottom surface of the second insulating cap layer 270. Drain regions 63 can be formed by depositing a doped semiconductor material within each recessed region above the dielectric cores 62. The drain regions 63 can have a doping of a second conductivity type that is the opposite of the first conductivity type. For example, if the first conductivity type is p-type, the second conductivity type is n-type, and vice versa. The dopant concentration in the drain regions 63 can be in a range from 5.0×10¹⁸/cm³ to 2.0×10²¹/cm³, although lesser and greater dopant concentrations can also be employed. The doped semiconductor material can be, for example, doped polysilicon. Excess portions of the deposited semiconductor material can be removed from above the top surface of the second insulating cap layer 270, for example, by chemical mechanical planarization (CMP) or a recess etch to form the drain regions 63.

Each combination of a memory film 50 and a vertical semiconductor channel 60 (which is a vertical semiconductor channel) within a memory opening 49 constitutes a memory stack structure 55. The memory stack structure 55 is a combination of a semiconductor channel, a tunneling dielectric layer, a plurality of memory elements as embodied as portions of the charge storage layer 54, and an optional blocking dielectric layer 52. Each combination of a pedestal channel portion 11 (if present), a memory stack structure 55, a dielectric core 62, and a drain region 63 within a memory opening 49 constitutes a memory opening fill structure 58. Each combination of a pedestal channel portion 11 (if present), a memory film 50, a vertical semiconductor channel 60, a dielectric core 62, and a drain region 63 within each support opening 19 fills the respective support openings 19, and constitutes a primary support pillar structure 20.

The first-tier structure (132, 142, 170, 165), the second-tier structure (232, 242, 270, 265), the inter-tier dielectric layer 180, the memory opening fill structures 58, and the primary support pillar structures 20 collectively constitute a memory-level assembly. The memory-level assembly is formed over the substrate semiconductor layer 9 such that the substrate semiconductor layer 9 includes horizontal semiconductor channels electrically connected to vertical semiconductor channels 60 within the memory stack structures 55.

Referring to FIGS. 10A and 10B, the first exemplary structure is illustrated after formation of a memory opening fill structure 58 within each memory opening 49 and formation of a primary support pillar structure 20 within each support opening 19. Each memory opening fill structure 58 comprises a respective vertical semiconductor channel 60.

Referring to FIGS. 11A-11C, a first contact-level dielectric layer 280 can be formed over the memory-level assembly. The first contact-level dielectric layer 280 is formed at a contact level through which various contact via structures are subsequently formed to the drain regions 63 and the various electrically conductive layers that replaces the sacrificial material layers (142, 242) in subsequent processing steps.

Backside trenches 79 are subsequently formed through the first contact-level dielectric layer 280 and the memory-level assembly. For example, a photoresist layer can be applied and lithographically patterned over the first contact-level dielectric layer 280 to form elongated openings that extend along a first horizontal direction hd1. An anisotropic etch is performed to transfer the pattern in the patterned photoresist layer through the first contact-level dielectric layer 280 and the memory-level assembly to a top surface of the substrate semiconductor layer 9. The photoresist layer can be subsequently removed, for example, by ashing.

The backside trenches 79 extend along the first horizontal direction hd1, and thus, are elongated along the first horizontal direction hd1. The backside trenches 79 can be laterally spaced among one another along a second horizontal direction hd2, which can be perpendicular to the first horizontal direction hd1. The backside trenches 79 can extend through the memory array region (e.g., a memory plane) 100 and the contact region 200 within each plane (P0-P7).

In one embodiment, the backside trenches 79 can laterally extend along the first horizontal direction hd1, and are laterally spaced apart along the second horizontal direction hd2. In one embodiment, the planes (P0-P7) may be arranged such that each even-numbered plane (P0, P2. P4, P6) is laterally spaced from a respective odd-numbered plane (P1, P3, P5, P7) by a respective backside trench 79, which is herein referred to as an inter-array backside trench 793. Generally, the backside trenches 79 may include first backside trenches 791 laterally extending through a respective one of the even-numbered planes (P0, P2, P4, P6), second backside trenches 792 laterally extending through a respective one of the odd-numbered planes (P1, P3, P5, P7), and inter-array backside trenches 793 formed within a respective gap region G (illustrated in FIG. 1B). The first and second backside trenches (791, 792) separate memory blocks within each respective plane. Generally, the first backside trenches 791, the second backside trenches 792, and the inter-array backside trenches 793 can be formed simultaneously by forming a patterned etch mask layer (not shown) over the at least one vertically alternating sequence continuous insulating layers (132, 232) and continuous sacrificial material layers (142, 242), and by anisotropically etching unmasked portions of the at least one vertically alternating sequence by performing an anisotropic etch process. In one embodiment, the patterned etch mask layer may be a patterned photoresist layer. In one embodiment, the first backside trenches 791, the second backside trenches 792, and the inter-array backside trenches 793 may have a same width along the second horizontal direction hd2. In one embodiment, the first backside trenches 791, the second backside trenches 792, and the inter-array backside trenches 793 may be formed as a periodic one-dimensional array that is repeated along the second horizontal direction hd2 with periodicity.

The portions of the continuous insulating layers (132, 232) that are divided by the first backside trenches 791 are herein referred to as first insulating layers (132, 232). The portions of the continuous insulating layers (132, 232) that are divided by the second backside trenches 792 are herein referred to as second insulating layers (132, 232). The portions of the continuous sacrificial material layers (142, 242) that are divided by the first backside trenches 791 are herein referred to as first sacrificial material layers (142, 242). The portions of the continuous sacrificial material layers (142, 242) that are divided by the second backside trenches 792 are herein referred to as second sacrificial material layers (142, 242).

Generally, the vertically alternating sequence of continuous insulating layers (132, 232) and continuous sacrificial material layers (142, 242) are separated into first alternating stacks of first insulating layers (132, 232) and first sacrificial material layers (142, 242) that are laterally spaced apart by the first backside trenches 791, and second alternating stacks of second insulating layers (132, 232) and second sacrificial material layers (142, 242) that are laterally spaced apart by second backside trenches 792. The first alternating stacks and the second alternating stacks are laterally spaced apart by an inter-array backside trench 793. A first subset of the memory opening fill structures 58 vertically extends through a respective one of the first alternating stacks, and a second subset of the memory opening fill structures 58 vertically extends through a respective one of the second alternating stacks.

Dopants of a second conductivity type, which is the opposite of the first conductivity type of the substrate semiconductor layer 9, can be implanted into a surface portion of the substrate semiconductor layer 9 to form a source region 61 underneath the bottom surface of each backside trench 79.

Referring to FIGS. 12A and 12B, an etchant that selectively etches the materials of the first and second-tier sacrificial material layers (142, 242) with respect to the materials of the first and second-tier insulating layers (132, 232), the first and second insulating cap layers (170, 270), and the material of the outermost layer of the memory films 50 can be introduced into the backside trenches 79, for example, employing an isotropic etch process. First backside recesses 143 are formed in volumes from which the first-tier sacrificial material layers 142 are removed. Second backside recesses 243 are formed in volumes from which the second-tier sacrificial material layers 242 are removed. In one embodiment, the first and second-tier sacrificial material layers (142, 242) can include silicon nitride, and the materials of the first and second-tier insulating layers (132, 232), can be silicon oxide. In another embodiment, the first and second-tier sacrificial material layers (142, 242) can include a semiconductor material such as germanium or a silicon-germanium alloy, and the materials of the first and second-tier insulating layers (132, 232) can be selected from silicon oxide and silicon nitride.

The isotropic etch process can be a wet etch process employing a wet etch solution, or can be a gas phase (dry) etch process in which the etchant is introduced in a vapor phase into the backside trench 79. For example, if the first and second-tier sacrificial material layers (142, 242) include silicon nitride, the etch process can be a wet etch process in which the first exemplary structure is immersed within a wet etch tank including phosphoric acid, which etches silicon nitride selective to silicon oxide, silicon, and various other materials employed in the art. In case the sacrificial material layers (142, 242) comprise a semiconductor material, a wet etch process (which may employ a wet etchant such as a KOH solution) or a dry etch process (which may include gas phase HCl) may be employed.

Each of the first and second backside recesses (143, 243) can be a laterally extending cavity having a lateral dimension that is greater than the vertical extent of the cavity. In other words, the lateral dimension of each of the first and second backside recesses (143, 243) can be greater than the height of the respective backside recess. A plurality of first backside recesses 143 can be formed in the volumes from which the material of the first-tier sacrificial material layers 142 is removed. A plurality of second backside recesses 243 can be formed in the volumes from which the material of the second-tier sacrificial material layers 242 is removed. Each of the first and second backside recesses (143, 243) can extend substantially parallel to the top surface of the substrate, which may be a top surface of the substrate semiconductor layer 9. A backside recess (143, 243) can be vertically bounded by a top surface of an underlying insulating layer (132 or 232) and a bottom surface of an overlying insulating layer (132 or 232). In one embodiment, each of the first and second backside recesses can have a uniform height throughout.

In one embodiment, a sidewall surface of each pedestal channel portion 11 can be physically exposed at each bottommost first backside recess after removal of the first and second-tier sacrificial material layers (142, 242). Further, a top surface of the substrate semiconductor layer 9 can be physically exposed at the bottom of each backside trench 79. An annular dielectric spacer 116 can be formed around each pedestal channel portion 11 by oxidation of a physically exposed peripheral portion of the pedestal channel portions 11. Further, a semiconductor oxide portion (not shown) can be formed from each physically exposed surface portion of the substrate semiconductor layer 9 concurrently with formation of the annular dielectric spacers.

Referring to FIGS. 13A-13B, a backside blocking dielectric layer (not shown) can be optionally deposited in the backside recesses and the backside trenches 79 and over the first contact-level dielectric layer 280. The backside blocking dielectric layer can be deposited on the physically exposed portions of the outer surfaces of the memory stack structures 55. The backside blocking dielectric layer includes a dielectric material such as a dielectric metal oxide, silicon oxide, or a combination thereof. If employed, the backside blocking dielectric layer can be formed by a conformal deposition process such as atomic layer deposition or chemical vapor deposition. The thickness of the backside blocking dielectric layer can be in a range from 1 nm to 60 nm, although lesser and greater thicknesses can also be employed.

At least one conductive material can be deposited in the plurality of backside recesses, on the sidewalls of the backside trench 79, and over the first contact-level dielectric layer 280. The at least one conductive material can include at least one metallic material, i.e., an electrically conductive material that includes at least one metallic element.

A plurality of first-tier electrically conductive layers 146 can be formed in the plurality of first backside recesses 143, a plurality of second-tier electrically conductive layers 246 can be formed in the plurality of second backside recesses 243, and a continuous metallic material layer (not shown) can be formed on the sidewalls of each backside trench 79 and over the first contact-level dielectric layer 280. Thus, the first and second-tier sacrificial material layers (142, 242) can be replaced with the first and second conductive material layers (146, 246), respectively. Specifically, each first-tier sacrificial material layer 142 can be replaced with an optional portion of the backside blocking dielectric layer and a first-tier electrically conductive layer 146, and each second-tier sacrificial material layer 242 can be replaced with an optional portion of the backside blocking dielectric layer and a second-tier electrically conductive layer 246. A backside cavity is present in the portion of each backside trench 79 that is not filled with the continuous metallic material layer.

The metallic material can be deposited by a conformal deposition method, which can be, for example, chemical vapor deposition (CVD), atomic layer deposition (ALD), electroless plating, electroplating, or a combination thereof. The metallic material can be an elemental metal, an intermetallic alloy of at least two elemental metals, a conductive nitride of at least one elemental metal, a conductive metal oxide, a conductive doped semiconductor material, a conductive metal-semiconductor alloy such as a metal silicide, alloys thereof, and combinations or stacks thereof. Non-limiting exemplary metallic materials that can be deposited in the backside recesses include tungsten, tungsten nitride, titanium, titanium nitride, tantalum, tantalum nitride, cobalt, and ruthenium. In one embodiment, the metallic material can comprise a metal such as tungsten and/or metal nitride. In one embodiment, the metallic material for filling the backside recesses can be a combination of titanium nitride layer and a tungsten fill material. In one embodiment, the metallic material can be deposited by chemical vapor deposition or atomic layer deposition.

Residual conductive material can be removed from inside the backside trenches 79. Specifically, the deposited metallic material of the continuous metallic material layer can be etched back from the sidewalls of each backside trench 79 and from above the first contact-level dielectric layer 280, for example, by an anisotropic or isotropic etch. Each remaining portion of the deposited metallic material in the first backside recesses constitutes a first-tier electrically conductive layer 146. Each remaining portion of the deposited metallic material in the second backside recesses constitutes a second-tier electrically conductive layer 246. Each electrically conductive layer (146, 246) can be a conductive line structure.

A subset of the second-tier electrically conductive layers 246 located at the levels of the drain-select-level dielectric isolation structures 72 constitutes drain select gate electrodes. A subset of the first-tier electrically conductive layers 146 located at each level of the annular dielectric spacers (not shown) constitutes source select gate electrodes. A subset of the electrically conductive layer (146, 246) located between the drain select gate electrodes and the source select gate electrodes can function as combinations of a control gate and a word line located at the same level. The control gate electrodes within each electrically conductive layer (146, 246) are the control gate electrodes for a vertical memory device including the memory stack structure 55.

Each of the memory stack structures 55 comprises a vertical stack of memory elements located at each level of the electrically conductive layers (146, 246). A subset of the electrically conductive layers (146, 246) can comprise word lines for the memory elements. The memory-level assembly is located over the substrate semiconductor layer 9. The memory-level assembly includes at least one vertically alternating sequence (132, 146, 232, 246) and memory stack structures 55 vertically extending through the at least one vertically alternating sequence (132, 146, 232, 246). Each alternating stack (132, 146, 232, 246) includes alternating layers of respective insulating layers (132, 232) and respective electrically conductive layers (146, 246). Each alternating stack (132, 146, 232, 246) comprises a staircase region that includes terraces in which each underlying electrically conductive layer (146, 246) extends farther along the first horizontal direction hd1 than any overlying electrically conductive layer (146, 246) in the memory-level assembly. Generally, the first sacrificial material layers 142 and the second sacrificial material layers 242 can be replaced with the first electrically conductive layers 146 and the second electrically conductive layers 246, respectively.

Referring to FIGS. 14A-14C, a backside trench fill structure 76 can be formed in the remaining volume of each backside trench 79. In the embodiment shown in FIGS. 14A-14C and 42-44A, the backside trench fill structure 76 consists of a dielectric separator. The dielectric separated may be formed, for example, by deposition of at least one dielectric material and removal of excess portions of the deposited at least one dielectric material from above a horizontal plane including the top surface of the first contact-level dielectric layer 280 by a planarization process such as chemical mechanical planarization or a recess etch.

In an alternative embodiment illustrated in FIGS. 18A to 21 , the backside trench fill structure 76 comprises a backside insulating spacer 74 and an electrically conductive local interconnect (e.g., source contact) 75. The backside insulating spacer 74 may be formed by depositing a relatively thin dielectric layer in the backside trench 79 followed by performing an anisotropic sidewall spacer etch to remove horizontal portions of the dielectric layer and leave the backside insulating spacer 74 on sidewalls of the backside trench 79. An electrically conductive material (e.g., metal, metal nitride, metal silicide or heavily doped semiconductor) is then deposited on the backside insulating spacer 74 and planarized to the top surface of the first contact-level dielectric layer 280 to form the local interconnect 75.

The backside trench fill structure 76 provide electrical isolation in all lateral directions, and are laterally elongated along the first horizontal direction hd1. As such, the backside trench fill structure 76 are laterally elongated along the first horizontal direction hd1. As used herein, a structure is “laterally elongated” if the maximum lateral dimension of the structure along a first horizontal direction is greater than the maximum lateral dimension of the structure along a second horizontal direction that is perpendicular to the first horizontal direction at least by a factor of 5.

The backside trench fill structures 76 can include first backside trench fill structures 761 filling the first backside trenches 791, second backside trench fill structures 762 filling the second backside trenches 792, and inter-array backside trench fill structures 763 filling the inter-array backside trenches 793. Generally, the first backside trench fill structures 761, the second backside trench fill structures 762, and the inter-array backside trench fill structure 762 can be formed by depositing at least a dielectric material and optionally a conductive material (such as a metallic material) within the first backside trenches 791, the second backside trenches 792, and the inter-array backside trenches 793 simultaneously. An inter-array backside insulating material portion (such as an backside insulating spacer 74) can be deposited within each inter-array backside trench 793 directly on a sidewall of one of the first alternating stacks of a first plane including a first three-dimensional memory array, and directly on a sidewall of one of the second alternating stacks of a second plane including a second three-dimensional memory array.

Referring to FIGS. 15A and 15B, a second contact-level dielectric layer 282 can be optionally formed over the first contact-level dielectric layer 280. The second contact-level dielectric layer 282 includes a dielectric material such as silicon oxide or silicon nitride. The thickness of the second contact-level dielectric layer 282 can be in a range from 30 nm to 300 nm, although lesser and greater thicknesses can also be employed.

A photoresist layer (not shown) can be applied over the second contact-level dielectric layer 282, and can be lithographically patterned to form openings at locations at which various contact via structures are to be subsequently formed. The openings in the photoresist layer include word line contact openings that overlie horizontal surfaces of the first and second stepped surfaces in the contact region 200. Further, the openings in the photoresist layer include drain contact openings that overlie top surfaces of the memory stack structures 55.

A reactive ion etch process is performed to transfer the pattern of the openings in the photoresist layer through underlying dielectric material layers. Contact via cavities are formed through underlying dielectric material portions (282, 280, 270, 265, 165). The contact via cavities include drain contact via cavities that are formed through the second contact-level dielectric layer 282, the first contact-level dielectric layer 280, and the second insulating cap layer 270 above top surfaces of the drain regions 63 within the memory stack structures 55. Top surfaces of the drain regions 63 are physically exposed at the bottom of the drain contact via cavities. The contact via cavities further include word line contact via cavities that are formed through the second contact-level dielectric layer 282, the first contact-level dielectric layer 280, the second insulating cap layer 270, and the second and first retro-stepped dielectric material portions (165, 265) by the anisotropic etch process. Top surfaces of the first and second-tier electrically conductive layers (146, 246) are physically exposed at bottom regions of the word line contact via cavities.

At least one conductive material can be deposited in the contact via cavities. Excess portions of the at least one conductive material can be removed from above a horizontal plane including the top surface of the second contact-level dielectric layer 282 by a planarization process such as a recess etch process or a chemical mechanical planarization (CMP) process. Each remaining portion of the at least one conductive material in the word line contact via cavities constitutes a layer contact via structure 86, and each remaining portion of the at least one conductive material in the drain contact via cavities constitutes a drain contact via structure 88.

First contact via structures 86 within a first subset of the layer contact via structures 86 vertically extend through the second retro-stepped dielectric material portion 265 and the first retro-stepped dielectric material portion 165 and contact a top surface of a respective one of the first-tier electrically conductive layers 146. Second contact via structures 86 within a second subset of the layer contact via structures 86 vertically extend through the second retro-stepped dielectric material portion 265 and contact a top surface of a respective one of the second-tier electrically conductive layers 246.

Referring to FIGS. 16A-16D, at least one upper interconnect level dielectric layer 284 can be formed over the contact-level dielectric layers (280, 282). Various upper interconnect level metal structures can be formed in the at least one upper interconnect level dielectric layer 284. For example, the various upper interconnect level metal structures can include line-level metal interconnect structures (96, 98). The line-level metal interconnect structures (96, 98) can include bit lines 98 that contact a respective one of the drain contact via structures 88 and extend along the second horizontal direction (e.g., bit line direction) hd2 and perpendicular to the first horizontal direction (e.g., word line direction) hd1. It is noted that only two subsets of the bit lines 98 are illustrated within each plane (P0-P7), and some bit lines 98 are schematically indicated as dotted lines between two sets of bit lines 98 within each plane (P0-P7). Further, the line-level metal interconnect structures (96, 98) can include upper metal line structures 96 that contact a top surface of a respective one of the layer contact via structures 86 and/or another contact via structure (not shown) that vertically extend through the retro-stepped dielectric material portions (165, 265) or other dielectric material portions (not shown). Additional metal interconnect structures (not shown) and additional dielectric material layers (not shown) may be formed to provide electrical interconnection among the various components of a three-dimensional memory device in the first exemplary structure.

In one embodiment shown in FIG. 16C, the bit lines 98 include first bit lines 981 formed within even-numbered planes (P0. P2, P4, P6) and second bit lines 98 formed within odd-numbered planes (P1, P3, P5, P7). Generally, the first bit lines 981 and the second bit lines 982 can be formed over the first alternating stacks of first insulating layers (132, 232) and first electrically conductive layers (146, 246) within each even-numbered plane (P0, P2, P4, P6), and over the second alternating stacks of second insulating layers (132, 232) and second electrically conductive layers (146, 246) within each odd-numbered plane (P1, P3, P5, P7). The first bit lines 981 are electrically connected to a respective subset of the first vertical semiconductor channels 60 within a respective first three-dimensional memory array in a respective one of the even-numbered planes (P0, P2, P4, P6), and are electrically isolated from the second vertical semiconductor channels 60 within any other three-dimensional memory array. The second bit lines 982 are electrically connected to a respective subset of the second vertical semiconductor channels 60 within a respective second three-dimensional memory array in a respective one of the odd-numbered planes (P1, P3, P5, P7), and are electrically isolated from the first vertical semiconductor channels 60 within any other three-dimensional memory array.

In an alternative embodiment, the bit lines 98 may extend across both the even and odd numbered planes, as shown in FIG. 16D. Each bit line 98 can be formed over the alternating stacks of insulating layers (132, 232) and electrically conductive layers (146, 246) within one even-numbered plane (P0, P2, P4, P6) and one odd-numbered plane (P1, P3, P5, P7). The bit lines 98 are electrically connected to vertical semiconductor channels 60 in a respective one of the even-numbered planes (P0, P2, P4, P6), and in a respective one of the odd-numbered planes (P1, P3, P5, P7).

Referring to FIGS. 17A and 17B, a logic die 700 according to an embodiment of the present disclosure is illustrated. The logic die 700 can include a logic-die substrate 708 and a peripheral circuit 710 formed thereupon. The logic-die substrate 708 includes a logic-die substrate semiconductor layer 709 at least at an upper portion thereof. Shallow trench isolation structures 720 may be formed in an upper portion of the logic-die substrate semiconductor layer 709 to provide electrical isolation from other semiconductor devices. The peripheral circuit 710 may include, for example, field effect transistors including respective transistor active regions 742 (i.e., source regions and drain regions), channel regions 746, and gate structures 750. The field effect transistors may be arranged in a CMOS configuration. Each gate structure 750 may include, for example, a gate dielectric 752, a gate electrode 754, a dielectric gate spacer 756 and a gate cap dielectric 758.

The logic die 700 can have multiple plane peripheral (i.e., driver or control) circuit (Q0-Q7), each of which can have the same area as a corresponding plane (P0-P7) of the semiconductor die illustrated in FIGS. 16C-16D. The logic die 700 may be one of a plurality of logic dies 700 provided over a semiconductor wafer. Each plane peripheral circuit (Q0-Q7) of the logic die 700 includes a peripheral circuit 710 configured to operate a respective three-dimensional memory array within one of the planes (P0-P7) of the semiconductor die illustrated in FIGS. 16C-16D. In one embodiment, each plane peripheral circuit (Q0-Q7) of the logic die 700 may include a word line driver circuit 620 that includes word line switching transistors, a bit line driver circuit 630 that includes sense amplifiers, and miscellaneous peripheral circuits 610 that are employed for operation of a respective three-dimensional memory array in the respective plane to be subsequently electrically connected thereto.

Dielectric material layers are formed over the semiconductor devices, which are herein referred to as dielectric material layers 760. The dielectric material layers 760 may include, for example, a dielectric liner 762 (such as a silicon nitride liner that blocks diffusion of mobile ions and/or apply appropriate stress to underlying structures), interconnect dielectric layers 764 that overlie the dielectric liner 762, a silicon nitride layer (e.g., hydrogen diffusion barrier) 766 that overlies the interconnect dielectric layers 764, and a bonding-pad-level dielectric layer 768.

The dielectric material layers 760 function as a matrix for metal interconnect structures 780 that provide electrical connection between the peripheral circuit 710 and logic-side bonding pads 798. The logic-side bonding pads 798 are embedded within the bonding-pad-level dielectric layer 768. Each dielectric material layer within the interconnect dielectric layers 764 may include any of doped silicate glass, undoped silicate glass, organosilicate glass, silicon nitride, silicon oxynitride, and dielectric metal oxides (such as aluminum oxide). In one embodiment, the interconnect dielectric layers 764 may comprise, or consist essentially of, dielectric material layers having dielectric constants that do not exceed the dielectric constant of undoped silicate glass (silicon oxide) of 3.9. The metal interconnect structures 780 are formed within the dielectric layer stack of the lower-level dielectric material layers 760. The metal interconnect structures 780 may include various metal via structures 786 and various metal line structures 788.

Generally, the logic die 700 includes a support circuitry configured to control operation of the memory die 900 containing the three-dimensional memory arrays within the planes (P0-P7) of FIGS. 16A-16D. The logic-side bonding pads 798 can have a mirror image pattern of a pattern of the memory-side bonding pads 998 shown in FIGS. 18A and 18B.

Referring to FIGS. 18A and 18B, the logic die 700 can be bonded to the memory die 900 of FIGS. 16A-16D. In FIG. 18A, the substrate semiconductor layer 9 comprises a doped top portion of a semiconductor (e.g., silicon) substrate 8, such as a doped well in a silicon substrate. In FIG. 18B, the substrate semiconductor layer 9 comprises a buried source line (e.g., a heavily doped polysilicon layer) located between the substrate (e.g., silicon wafer) 8 and the first-tier alternating stack (132, 146).

For example, wafer-to-wafer bonding can be employed to bond a first wafer including a plurality of instances of the semiconductor die of FIGS. 16A-16D to a second wafer including a plurality of instances of the logic die 700. The logic-side bonding pads 798 are bonded to a respective one of the memory-side bonding pads 998 through metal-to-metal bonding. In case the bonding-pad-level dielectric layer 768 and the topmost dielectric layer 968 of the memory die 900 include silicon oxide, oxide-to-oxide bonding may be used in addition to, or in lieu of, metal-to-metal bonding.

Generally, the logic-side bonding pads 798 can be bonded to a respective one of the memory-side bonding pads 998. The logic die 700 includes a support circuitry (i.e., a peripheral circuit) configured to control operation of the three-dimensional memory device within the memory die 900. If the configuration of FIG. 16C is used, then an optional cut region CR shown in FIG. 23 can be provided at a bit line level between first bit lines 981 and second bit lines 982 of a neighboring pair of adjacent even and odd planes. Alternatively, if the configuration of FIG. 16D is used, then the cut region is omitted and each bit line 98 extends continuously over adjacent odd and even planes, as shown in FIGS. 18A and 18B. The lateral spacing between the neighboring pair of planes that employ different sets of bit lines 98 can be the same as the width of a backside trench fill structure 76.

Generally, the bit lines 98 may contact a respective subset of the drain contact via structures 88 directly, or may be electrically connected to a respective subset of the drain contact via structures 88 through additional connection via structures 188.

Generally, an alternating stack of insulating layers (132, 232) and spacer material layers, such as sacrificial material layers (142, 242), can be formed over a substrate. The spacer material layers may be formed as, or may be subsequently replaced with, electrically conductive layers (146, 246). Groups of memory openings 49 can be formed through the alternating stack (132, 232). Groups of memory opening fill structures 58 can be formed in the memory openings 49. Each of the of memory opening fill structures 58 includes a memory stack structure 55, which includes a respective vertical stack of memory elements (which may comprise portions of the memory film 50 located at levels of electrically conductive layers (146, 246)) and a respective vertical semiconductor channel 60. Each of the memory opening fill structures 58 may comprise a vertical NAND string containing a vertical stack of memory elements. Alternating stacks of insulating layers (132, 132) and electrically conductive layers (146, 246) can be formed over the substrate. Backside trench fill structures 76 can be formed through the alternating stacks {(132, 146), (232, 246)}. For each alternating stack of insulating layers (132, 232) and electrically conductive layers (146, 246), a pair of backside trench fill structures 76 can be formed through the alternating stack {(132, 146), (232, 246)}.

Referring to FIGS. 19A and 19B, the backside of the substrate 8 may be thinned, for example, by grinding, polishing, an anisotropic etch process, and/or an isotropic etch process. The thickness of the substrate semiconductor layer 9 (i.e., a doped well in FIG. 19A or a buried source line in FIG. 19B) after thinning may be in a range from 100 nm to 6,000 nm, although lesser and greater thicknesses may also be employed. In one embodiment shown in FIG. 19A, the substrate semiconductor layer 9 may be a single crystalline semiconductor material layer such as a single crystalline silicon layer. In another embodiment shown in FIG. 19B, the substrate semiconductor layer 9 may be a polycrystalline semiconductor material layer, such as a doped polysilicon layer. The substrate semiconductor layer 9 constitutes a source-level material layer (e.g., a source line). In one embodiment, the source-level material layer may be doped with dopants of the second conductivity type by providing dopants of the second conductivity type, for example, by ion implantation or gas phase diffusion. In an alternative embodiment, dopants of the second conductivity type may be implanted or diffused from the front side of the substrate semiconductor layer 9 prior to formation of the first-tier alternating stack of the first-tier insulating layers 132 and the first-tier sacrificial material layers 142. In another alternative embodiment shown in FIG. 19B, dopants of the second conductivity type may be provided in-situ during growth of the buried source line.

Referring to FIGS. 20A and 20B, a photoresist layer can be applied over the backside of the substrate semiconductor layer 9, and can be lithographically patterned to form line-shaped openings that laterally extend along the first horizontal direction hd1. An anisotropic etch process can be performed to divide the substrate semiconductor layer 9 into a plurality of semiconductor material layers, which function as a source region (or combination of source region and source line) for a respective group of vertical semiconductor channels 60 located within the same area (e.g., a string unit area). The plurality of semiconductor material layers are hereafter referred to as source layers 9. The thinned substrate semiconductor layer 9 having a doping of the second conductivity type functions as a source-level material layer, and a plurality of source layers 9 are formed by patterning the thinned substrate semiconductor layer 9. A plurality of source-side trenches 21 are formed through the source-level material layer, such that each neighboring pair of source layers 9 of the plurality of source layers 9 is laterally spaced from each other by a respective one of the plurality of source-side trenches 21. The plurality of source layers 9 is laterally spaced apart, and are electrically isolated from each other. Each group of memory opening fill structures 58 contacts a respective one of the plurality of source layers 9. Each neighboring pair of source layers 9 of the plurality of source layers 9 is laterally spaced from each other by a respective one of the plurality of source-side trenches 21. A dielectric material may be deposited in the source-side trenches 21 and over the source layers 9 to form source-level dielectric isolation structures 23 located in the respective trenches 21.

Referring to FIG. 21 , a first alternative configuration of the first exemplary structure is illustrated after formation of a plurality of source layers 9 (e.g., of the type shown in FIG. 18A or buried source line shown in FIG. 18B). In the first alternative configuration, the plurality of source-side trenches 21 are extended through both the source-level material layer to form the source layers 9 and through at least one top most electrically conductive layer 146 underlying the source layers 9 to form separated source-side select gate electrodes (SGS) (i.e., source-side select gate lines) 146S. Each patterned first-tier electrically conductive layer 146 within the first subset of the electrically conductive layers (146, 246) can be divided into a plurality of source-side select gate electrodes 146S by forming the source-side trenches 21. The source-side trenches 21 do not divide a second subset of the electrically conductive layers which function as word lines (i.e., word lines) (146W, 246W) that laterally extend along the word line direction hd1 between a neighboring pair of backside trench fill structures 76. The source-side trenches 21 also do not divide the drain-side select gate electrodes 246D which are separated by the drain-select-level dielectric isolation structures 72. A dielectric material may be deposited in the source-side trenches 21 and over the source layers 9 to form source-level dielectric isolation structures 23 located in the respective trenches 21.

FIGS. 22A-22D illustrate an alternative configuration of a memory opening 49 during formation of a memory opening fill structure 58 according to a second embodiment of the present disclosure.

Referring to FIG. 22A, an inter-tier memory opening 49 (i.e., a memory opening 49) or an inter-tier support opening 19 is illustrated at the processing steps of FIG. 8 .

Referring to FIG. 22B, a blocking dielectric layer 52, a charge storage layer 54, and a tunneling dielectric layer 56 can be deposited in the inter-tier memory opening 49 by performing the processing steps of FIG. 9B. The combination of the blocking dielectric layer 52, the charge storage layer 54, and the tunneling dielectric layer 56 constitutes a memory film 50.

Referring to FIG. 23C, a semiconductor channel layer 60L can be deposited on the memory film 50. The semiconductor channel layer 60L can be deposited in the same manner as the first semiconductor channel layer 601 or the second semiconductor channel layer 602 described above, and may have the same material composition as the first semiconductor channel layer 601 and/or the second semiconductor channel layer 602. The thickness of the semiconductor channel layer 60L can be the same as the sum of the thickness of the first semiconductor channel layer 601 or the second semiconductor channel layer 602.

Referring to FIG. 22D, the processing steps of FIGS. 9F, 9G, and 9H can be performed to form a dielectric core 62 and a drain region 63 within each memory opening fill structure 58. Each remaining portion of the semiconductor channel layer 60L constitutes a vertical semiconductor channel 60.

Subsequently, the processing steps of FIGS. 10-18 can be performed to form a second exemplary structure including a bonded assembly of a memory die 900 and a logic die 700 according to a second embodiment of the present disclosure. Each alternating stack of insulating layers (132, 232) and electrically conductive layers (146, 246) can be laterally bounded by a pair of backside trench fill structures 76.

Referring to FIG. 23 , the optional cut region CR between the first and second bit lines 981 and 982 shown in FIG. 16C may be present in the memory die 900 between adjacent planes P0 and P1. Alternatively, the cut region CR may be omitted, and the continuous bit lines 98 shown in FIGS. 16D and 20 may be provided instead.

Referring to FIGS. 23 and 24A, the substrate semiconductor layer 9 can be removed from the backside of the bonded assembly, for example, by grinding, polishing, an anisotropic etch process, or an isotropic etch process. For example, the substrate semiconductor layer 9 may be thinned from the backside, for example, by grinding, and an isotropic etch process or an anisotropic etch process may be performed to remove remaining portions of the substrate semiconductor layer 9 selective to the memory films 50. For example, the isotropic etch process may include a wet etch process employing potassium hydroxide.

Referring to FIG. 24B, a sequence of isotropic etch processes can be performed to etch physically exposed portions (i.e., bottom portions) of the memory films 50. The sequence of isotropic etch processes can be selected to sequentially etch the materials of the blocking dielectric layers 52, the charge storage layers 54, and the tunneling dielectric layers 56 selective to the material of the vertical semiconductor channels 60 to expose at least the bottom portions of the vertical semiconductor channels 60.

Referring to FIGS. 25A and 25B, a source-level material layer 109 can be deposited on the physically exposed end surfaces of the vertical semiconductor channels 60, which are herein referred to as proximal end surfaces. The source-level material layer 109 includes at least one electrically conductive material. In one embodiment, the source-level material layer 109 comprises a heavily doped semiconductor material, such as polysilicon. In another embodiment, the source-level material layer 109 may include a vertical stack of a heavily doped polycrystalline source semiconductor (e.g., polysilicon) layer 109A having a doping of the second conductivity type, and a metallic source layer 109B, such as a metal silicide (e.g., titanium, tungsten, cobalt or nickel silicide) or a metal (e.g., tungsten, aluminum, molybdenum, copper, etc.). Generally, the source-level material layer 109 can be formed by replacing the substrate with at least one electrically conductive material layer.

Referring to FIGS. 26A and 26B, source-side trenches 21 can be formed though the source-level material layer 109. Each of the source-side trenches 21 can laterally extend along the first horizontal direction (i.e., word line direction) hd1, and can laterally divide the source-level material layer 109 into a plurality of source structures, which are herein referred to as source lines 109. A first subset of the source-side trenches 21A extend to the proximal subset of the first electrically conductive layers 146 that proximal to the source layers 109. An optional second subset of the source-side trenches 21B vertically extends to the backside trench fill structures 76. A dielectric material may be deposited in the source-side trenches 21 and over the source layers 9 to form source-level dielectric isolation structures 23 located in the respective trenches 21. FIG. 26A illustrates the split bit line (981, 982) configuration of FIG. 16C, while FIG. 26B illustrates the continuous bit line 98 configuration of FIG. 16D.

Referring to FIG. 27 , a circuit schematic of the second exemplary structure of FIGS. 26A and 26B is illustrated. FIG. 27 illustrates a 16 staggered row device for clarity, while FIGS. 26A and 26B illustrate the 24 staggered row device. The source lines (SL1, SL2, SL3, SL4) may comprise the source layers 109 illustrated in FIGS. 26A and 26B or the source layers 9 illustrated in FIG. 20A or 20B. By splitting a single source line into four source layers (e.g., source lines), a smaller erase unit EU having a smaller number of memory cells may be erased during an erase step (including a gate induced drain leakage (GIDL) erase step) during which the erase voltage is applied to a respective source line (e.g., SL1 in FIG. 27 ). Thus, the size of the functional memory block (i.e., erase unit EU) is reduced. This reduces the operational leakage current.

Referring collectively to the first exemplary structure and the second exemplary structure, a plurality of source layers (9 or 109) can be formed by patterning a source-level material layer. The plurality of source layers (9 or 109) are laterally spaced apart, and electrically isolated from each other, and each group of memory opening fill structures 58 can contact a respective one of the plurality of source layers (9 or 109). A plurality of source-side trenches 21 can be formed through the source-level material layer, wherein each neighboring pair of source layers of the plurality of source layers (9, 109) is laterally spaced from each other by a respective one of the plurality of source-side trenches 21.

Referring to FIG. 28 , a third exemplary structure according to a third embodiment of the present disclosure is illustrated after removal of the substrate semiconductor layer 9 and after formation of source-select-level trenches 17. In this case, the source-select-level trenches 17 may be formed through the first subset of the electrically conductive layers (i.e., the source-side select gate electrodes) 146S after removal of the substrate 8 and prior to formation of the at least one conductive material layer that is subsequently employed to form source layers 109. Generally, a plurality of source-side select gate electrodes (i.e., source-select-level electrically conductive layers) 146S can be formed by forming the source-select-level trenches 17 through the plurality of source-side select gate electrodes 146S prior to, or after, formation of the source-level material layer. The source-select-level trenches 17 do not divide the word lines (146W, 246W) or the drain-side select gate electrodes 146D. The source-select-level trenches 17 are source-side trenches that vertically extend through the source-side select gate electrodes 146S, which are a subset of the electrically conductive layers (146, 246). The source-side select gate electrodes 146S can activate or deactivate a respective string group of vertical semiconductor channels 60 of NAND strings, thereby selecting or deselecting NAND string groups within the three-dimensional memory array. While a split bit line 98 configuration is shown in FIG. 28 , it should be understood that the continuous bit line 98 configuration of FIG. 16D or 26B may be used instead.

Referring to FIG. 29 , a dielectric material such as silicon oxide can be deposited in the source-select-level trenches 17. Excess portions of the dielectric material can be removed from above the horizontal plane including a topmost one of the insulating layers (such as a most proximal first-tier insulating layer 132) by a planarization process. Source-select-level dielectric isolation structures 22 comprising remaining portions of the dielectric material can be formed in the source-select-level trenches 17.

Referring to FIG. 30 , the processing steps of FIGS. 25A and 25B can be performed to form a source-level material layer 109 on the physically exposed end surfaces of the vertical semiconductor channels 60, which are herein referred to as proximal end surfaces. The source-level material layer 109 includes at least one electrically conductive material. In one embodiment, the source-level material layer 109 may include a vertical stack of a polycrystalline source semiconductor layer 109A having a doping of the second conductivity type and a metallic source layer 109B including a metallic material. Generally, the source-level material layer 109 can be formed by replacing the substrate 8 with at least one conductive material layer 109. In the third embodiment, the source-side trenches 21 of FIGS. 26A and 26B may be present or omitted.

Referring to FIG. 31A, a circuit schematic of the third exemplary structure of FIG. 30 is illustrated. Four split source-side select gate electrodes 146S1, 146S2, 146S3 and 146S4 are illustrated in FIG. 31A. However, there may be two, three or more than four split source-side select gate electrodes. The single source line SL may comprise the source layer 9 illustrated in FIG. 20A or 20B or the source layer 109 illustrated in FIG. 29 . In this embodiment, a smaller erase unit EU having a smaller number of memory cells may be erased during an erase step during which the erase voltage is applied to the common source line SL. Thus, the size of the functional memory block (i.e., erase unit EU) is reduced. This reduces the operational leakage current.

Referring to FIG. 31B, a schematic top view diagram of the third exemplary structure is illustrated. A plurality of source-side select gate electrodes 146S that are located at a same vertical level are laterally spaced from each other by the source-select-level dielectric isolation structures 22 in the horizontal direction. The plurality of source-side select gate electrodes 146S are located between at least one source layer (9, 109) and the word lines (146W, 246W) in the vertical direction.

Referring to FIG. 32 , a fourth exemplary structure according to a fourth embodiment of the present disclosure is illustrated, which can be the same as the second exemplary structure of FIGS. 25A and 25B. The structure may include the split bit lines (981, 982) of FIG. 16C or the continuous bit line 98 of FIG. 16D.

Referring to FIG. 33 , source-side trenches 21 can be formed through the source-level material layer 109 and through a first subset of the electrically conductive layers (such as a proximal subset of the first-tier electrically conductive layers 146). The pattern of the source-side trenches 21 can be the same as the pattern of the source-side trenches in the exemplary structure illustrated in FIGS. 26A and 26B. A plurality of source layers 109 are formed by patterning the source-level material layer 109. The plurality of source layers 109 can be laterally spaced apart, and can be electrically isolated from each other. Each string group of memory opening fill structures 58 contacts a respective one of the plurality of source layers 109.

Each patterned first-tier electrically conductive layer 146 within the first subset of the electrically conductive layers (146, 246) can be divided into a plurality of source-side select gate electrodes 146S by forming source-side trenches 21. The source-side trenches do not divide the word lines (146W, 246W) or the drain-side select gate electrodes 246D. A dielectric material may be deposited in the source-side trenches 21 and over the source layers 109 to form source-level dielectric isolation structures 23 located in the respective trenches 21.

A first subset of the source-side trenches 21 extends into a respective one of the backside trench fill structures 76. A second subset of the source-side trenches 21 extends into and divides a proximal subset of one or more electrically conductive layers 146 into a respective plurality of source-side select gate electrodes 146S.

Referring to FIG. 34 , a first alternative configuration of the fourth exemplary structure according to the fourth embodiment of the present disclosure is illustrated. The first alternative configuration of the fourth exemplary structure can be derived from the fourth exemplary structure of FIG. 33 by depositing a dielectric material in the source-side trenches 21 and over the source layers 109 to form a source-level dielectric isolation layer 122, such that each portion of layer 122 that protrudes downward into the respective trench 21 comprises a combination of the source-level isolation structure 23 and the source-select-level isolation structure 22.

Referring to FIG. 35 , a second alternative configuration of the fourth exemplary structure according to the fourth embodiment of the present disclosure can be derived from the third exemplary structure of FIG. 30 by dividing the source-level material layer 109 and dividing the source-side select gate layer 146S in separate steps. For example, the source-select-level dielectric isolation structures 22 are formed in the source-side select gate layer 146S first as shown in FIG. 29 . The source-level material layer 109 is then deposited over the source-select-level dielectric isolation structures 22 and the source-side select gate layer 146S, followed by forming the source-side trenches 21 in the source-level material layer 109 to divide layer 109 into the plurality of source layers 109, using the method shown in FIGS. 26A and 26B. A dielectric material may be deposited in the source-side trenches 21 and over the source layers 9 to form source-level dielectric isolation structures 23 located in the respective trenches 21.

Referring to FIG. 36 , a circuit schematic of various configurations of the fourth exemplary structure of FIGS. 32-35 is illustrated. A plurality of split source lines (SL1, SL2, SL3, SL4) and a plurality of split source-side select gate electrodes (146S1, 146S2, 146S3, 146S4) can be formed between a pair of backside trench fill structures 76. Each block of vertical NAND strings can be activated or deactivated by a source layer (9, 109), by a source-side select gate electrode 146S, or by a combination of a source layer and a source-side select gate electrode 146S.

Referring to FIG. 37 , an exemplary structure for providing electrical connections to a source layer (9 or 109) is illustrated according to an embodiment of the present disclosure. Specifically, backside metal interconnect structures 930, such as an aluminum strap, can be employed to provide electrical connection between metal interconnect structures 980A (that are a subset of structures 980 described above) and each source layer (9 or 109). A subset of the backside metal interconnect structures 930 can contact a backside surface of a respective one of the source layers (9 or 109).

Referring to FIG. 38 , another exemplary structure for providing electrical connections to a source layer (9 or 109) is illustrated according to an embodiment of the present disclosure. In this case, metal interconnect structures 980A may contact a front-side surface of a respective one of the source layers (9 or 109).

Referring to FIGS. 39A and 39B, a fifth exemplary structure according to a fifth embodiment of the present disclosure can be derived from the first exemplary structure of FIGS. 10A and 10B by modifying the pattern of the memory opening fill structures 58. Specifically, the memory openings 49 and the memory opening fill structures 58 can be formed on-pitch so that all memory opening fill structures 58 remain active after formation of drain-select-level dielectric isolation structures 72. In contrast, in the first exemplary structure of FIGS. 10A and 10B, each fifth row of memory opening fill structures 58 acts as a dummy memory opening fill structure 58 because it is cut in half by the respective drain-select-level dielectric isolation structure 72.

Referring to FIGS. 40A and 40B, drain-select-level dielectric isolation structures 72 can be formed through a distal subset of the second-tier sacrificial material layers 242 that are distal from the substrate semiconductor layer 9. In this case, the drain-select-level dielectric isolation structures 72 can be formed between a pair of rows of memory openings fill structures 58, and can cut through edge portions each memory opening fill structures 58 within the pair of rows of memory opening fill structures 58. Each drain-select-level dielectric isolation structure 72 can laterally extend along the first horizontal direction hd1.

Referring to FIGS. 41 and 42 , the processing steps of FIGS. 11-19 and the processing steps of FIG. 23 can be performed. In one embodiment, the processing steps of FIGS. 22A-22D may be employed to form each of the memory opening fill structures 58. In this case, a sequence of isotropic etch processes may be employed to remove proximal end portions of the memory films 50, and to physically expose proximal end portions of the vertical semiconductor channels 60.

Referring to FIG. 43 , a photoresist layer (not shown) can be applied over the physically exposed proximal surface of the alternating stacks {(132, 146), (232, 246)}, and can be lithographically patterned to form line-shaped openings within areas overlying the drain-select-level dielectric isolation structures 72. An anisotropic etch process can be performed to etch through a first subset of the electrically conductive layers (such as a proximal subset of the first-tier electrically conductive layers 146) to form source-side select gate electrodes 146S. Source-select-level trenches 17 can be formed through the first subset of the electrically conductive layers into the source-side select gate electrodes 146S.

Referring to FIGS. 44A and 44B, source-select-level dielectric isolation structures 22 can be formed in the source-select-level trenches 17 by depositing a dielectric material such as silicon oxide, and by removing excess portions of the dielectric material from above the alternating stack of insulating layers (132, 232) and electrically conductive layers (146, 246).

Referring to FIG. 45 , the processing steps of FIG. 32 can be performed to form a source-level material layer 109, which can function as a single source layer 109.

Referring to FIG. 46 , the processing steps of FIG. 35 can be optionally performed to divide the source-level material layer 109 into a plurality of source layers 109. A dielectric material may be deposited in the source-side trenches 21 and over the source layers 109 to form source-level dielectric isolation structures 23 located in the respective trenches 21. Generally, the plurality of source layers 109 can be formed by patterning the source-level material layer. The plurality of source layers 109 are laterally spaced apart, and are electrically isolated from each other. Each group of memory opening fill structures 58 contacts a respective one of the plurality of source layers 109.

Referring to all drawings and according to various embodiments of the present disclosure, a three-dimensional memory device comprises: an alternating stack of insulating layers (132, 232) and electrically conductive layers (146, 246) located over a plurality of source layers (9, 109), wherein the alternating stack is located between a pair of backside trench fill structures 76; memory openings 49 vertically extending through the alternating stack {(132, 146), (232, 246)}; and groups of memory opening fill structures 58 located in the memory openings 49, wherein each of the memory opening fill structures 58 includes a respective vertical stack of memory elements (which can comprise portions of the charge storage layers 54 located at levels of the word lines (146W, 246W)), a respective vertical semiconductor channel 60 having a first end that contacts a respective one of the plurality of source layers (9, 109), and a respective drain region 63 contacting a second end of the respective vertical semiconductor channel 60, wherein: the plurality of source layers (9, 109) are laterally spaced apart and electrically isolated from each other; and each group of memory opening fill structures 58 contacts a respective one of the plurality of source layers.

In one embodiment, the plurality of source layers 9 comprises a plurality of single crystalline semiconductor material layers having a same crystallographic orientation. In one embodiment, each of the memory opening fill structures 58 comprises a pedestal channel portion 11 comprising a single crystalline semiconductor material having a doping of an opposite conductivity type relative to the plurality of single crystalline semiconductor material layers, and contacting a respective one of the plurality of single crystalline semiconductor material layers.

In one embodiment, the plurality of source layers 109 comprises a plurality of polycrystalline source semiconductor layers 109A; and each of the memory opening fill structures 58 contacts a respective one of the plurality of polycrystalline source semiconductor layers 109A. In one embodiment, each of the plurality of source layers 109 comprises a respective stack of a source semiconductor layer 109A and a metallic source layer 109B.

In one embodiment, the plurality of source layers (9, 109) are laterally spaced apart from each other by respective source-level dielectric isolation structures 23. In one embodiment, the electrically conductive layers comprise: word lines (146W, 246W) which continuously laterally extend between and contact each of the pair of the backside trench fill structures 76; and a plurality of source-side select gate electrodes 146S located between the plurality of source layers (9, 109) and the word lines (146W, 246W) in a vertical direction. The plurality of the source-side select gate electrodes 146S are laterally spaced apart by source-select-level dielectric isolation structures 23.

In one embodiment, each of the source-level dielectric isolation structures 23 contacts a respective one of the source-select-level isolation structures 22. In the configuration of FIG. 21 , each of the source-level dielectric isolation structures 23 has vertically coincident sidewalls (i.e., continuous straight sidewalls having a continuous taper or no taper in the vertical direction) with the respective one of the source-select-level isolation structures. In the configuration of FIG. 35 , a horizontal step exists between each of the source-level dielectric isolation structures 23 and a respective one of the source-select-level isolation structures 22. In the configuration of FIG. 34 , a source-level isolation dielectric layer 120 contacts a backside of each of the plurality of source layers 109 and comprises vertically downward protruding portions 122 which include both the source-level dielectric isolation structures 23 and the source-select-level isolation structures 22.

In one embodiment, each of the plurality of source layers (9, 109) contacts only one of the pair of the backside trench fill structures 76 or does not contact any of the pair of the backside trench fill structures 76. In one embodiment, each of the plurality of source-side select gate electrodes 146S laterally surrounds a respective group of memory opening fill structures 58 and is laterally spaced from any other group of memory opening fill structures 58 of the group of memory opening fill structures 58.

In one embodiment, the three-dimensional memory device comprises bit lines 98 and drain contact via structures 88 contacting the drain regions 63. The electrically conductive layers (146, 246) comprise a plurality of drain-select-level electrically conductive layers 246D located between the word lines (146W, 246W) and the bit lines 98 in a vertical direction, and laterally spaced apart by drain-select-level dielectric isolation structures 72. In one embodiment, each of the pair of backside trench fill structures 76 comprises a dielectric structure or an electrically conductive local interconnect 75 surrounded by an insulating spacer 74, as shown in FIG. 18A.

According to another aspect of the present disclosure, a three-dimensional memory device comprises: an alternating stack of insulating layers (132, 232) and electrically conductive layers (146, 246) located over at least one source layer (9, 109) and located between a pair of backside trench fill structures 76; groups of memory openings 49 vertically extending through the alternating stack {(132, 146), (232, 246)}; and groups of memory opening fill structures 58 located in the groups of memory openings 49, wherein each of the memory opening fill structures 58 includes a respective vertical stack of memory elements (which comprise portions of the charge storage layers 54 located at levels of the word lines (146W, 246W), a respective vertical semiconductor channel 60 having a first end that contacts the at least one source layer (9, 109), and a respective drain region 63 contacting a second end of the respective vertical semiconductor channel 60. The electrically conductive layers (146, 246) comprise: word lines (146W, 246W) continuously laterally extending between, and contacting, each of the pair of the backside trench fill structures 76; and a plurality of source-side select gate electrodes 146S located between the at least one source layer (9, 109) and the word lines (146W, 246W) in a vertical direction, and located between the pair of backside trench fill structures 76 in a horizontal direction, wherein the plurality of source-side select gate electrodes 146S are laterally spaced apart by source-select-level dielectric isolation structures 22.

In one embodiment, the vertical semiconductor channels 60 comprise a semiconductor material having a doping of a first conductivity type; and the at least one source layer (9, 109) comprises a semiconductor material layer having a doping of a second conductivity type that is the opposite of the first conductivity type. In one embodiment, the at least one source layer (9, 109) comprises a continuous source layer that contacts each of the first end of each of the vertical semiconductor channels 60. In one embodiment, each of the source-select-level dielectric isolation structures 22 comprises a first horizontal surface that contacts one of the insulating layers (132, 232) and a second horizontal surface that contacts the at least one source layer (9, 109).

In another embodiment, the at least one source layer (9, 109) comprises a plurality of source layers that are laterally spaced apart from each other. Each group of memory opening fill structures 58 of the groups of memory opening fill structures 58 contacts a respective one of the plurality of source layers (9, 109) and is electrically isolated from all other source layers (9, 109) of the plurality of source layers (9, 109).

In one embodiment, the plurality of source layers (9, 109) are laterally spaced apart from each other by respective source-level dielectric isolation structures 23. In one embodiment, each of the source-level dielectric isolation structures 23 contacts a respective one of the source-select-level isolation structures 22. In the configuration of FIG. 21 , each of the source-level dielectric isolation structures 23 has vertically coincident sidewalls (i.e., continuous straight sidewalls having a continuous taper or no taper in the vertical direction) with the respective one of the source-select-level isolation structures. In the configuration of FIG. 35 , a horizontal step exists between each of the source-level dielectric isolation structures 23 and a respective one of the source-select-level isolation structures 22. In the configuration of FIG. 34 , a source-level isolation dielectric layer 120 contacts a backside of each of the plurality of source layers 109 and comprises vertically downward protruding portions 122 which include both the source-level dielectric isolation structures 23 and the source-select-level isolation structures 22.

In one embodiment, each of the pair of backside trench fill structures 76 comprises a dielectric structure or an electrically conductive local interconnect 75 surrounded by an insulating spacer 74, as shown in FIG. 18A.

In one embodiment, the plurality of source layers 109 comprises a plurality of polycrystalline semiconductor layers 109A. In one embodiment, each of the plurality of source layers (9, 109) contacts only one of the pair of the backside trench fill structures 76 or does not contact any of the pair of the backside trench fill structures 76. In one embodiment, each of the plurality of source-side select gate electrodes 146S laterally surrounds a respective group of memory opening fill structures 58 and is laterally spaced from any other group of memory opening fill structures 58 of the group of memory opening fill structures 58.

In one embodiment, by performing an erase operation on a smaller memory string rather than the entire memory block, the number of reprogramming steps are reduced. This improves the programming speed. Furthermore, the select/unselect operation is operated with higher precision on the string unit. The disturbed memory cell area of the erase unit EU is reduced. Thus, the unselected NAND string stress is reduced and cell degradation is improved.

Although the foregoing refers to particular embodiments, it will be understood that the disclosure is not so limited. It will occur to those of ordinary skill in the art that various modifications may be made to the disclosed embodiments and that such modifications are intended to be within the scope of the disclosure. Compatibility is presumed among all embodiments that are not alternatives of one another. The word “comprise” or “include” contemplates all embodiments in which the word “consist essentially of” or the word “consists of” replaces the word “comprise” or “include,” unless explicitly stated otherwise. Where an embodiment employing a particular structure and/or configuration is illustrated in the present disclosure, it is understood that the present disclosure may be practiced with any other compatible structures and/or configurations that are functionally equivalent provided that such substitutions are not explicitly forbidden or otherwise known to be impossible to one of ordinary skill in the art. All of the publications, patent applications and patents cited herein are incorporated herein by reference in their entirety. 

What is claimed is:
 1. A three-dimensional memory device, comprising: an alternating stack of insulating layers and electrically conductive layers located over a plurality of source layers, wherein the alternating stack is located between a pair of backside trench fill structures, wherein the electrically conductive layers comprise word lines and source-side select gate electrodes which are located between the plurality of source layers and the word lines in a vertical direction, source-side trenches extending through both the source-side select gate electrodes and the plurality of source layers, wherein the source-side trenches do not divide the word lines; groups of memory openings vertically extending through the alternating stack; and groups of memory opening fill structures located in the groups of memory openings, wherein each of the memory opening fill structures includes a respective vertical stack of memory elements, a respective vertical semiconductor channel having a first end that contacts a respective one of the plurality of source layers, and a respective drain region contacting a second end of the respective vertical semiconductor channel, wherein: the plurality of source layers are laterally spaced apart and electrically isolated from each other; and each group of memory opening fill structures contacts a respective one of the plurality of source layers.
 2. The three-dimensional memory device of claim 1, wherein the plurality of source layers comprises a plurality of single crystalline semiconductor material layers having a same crystallographic orientation.
 3. The three-dimensional memory device of claim 2, wherein each of the memory opening fill structures comprises a pedestal channel portion comprising a single crystalline semiconductor material having a doping of an opposite conductivity type relative to the plurality of single crystalline semiconductor material layers, and contacting a respective one of the plurality of single crystalline semiconductor material layers.
 4. The three-dimensional memory device of claim 1, wherein: the plurality of source layers comprises a plurality of polycrystalline source semiconductor layers; and each of the memory opening fill structures contacts a respective one of the plurality of polycrystalline source semiconductor layers.
 5. The three-dimensional memory device of claim 1, wherein each of the plurality of source layers comprises a respective stack of a source semiconductor layer and a metallic source layer.
 6. The three-dimensional memory device of claim 1, wherein: the plurality of source layers are laterally spaced apart from each other by respective source- level dielectric isolation structures that fill the source-side trenches; and each of the source-side select gate electrodes comprises a respective sidewall that contacts one of the source-level dielectric isolation structures.
 7. The three-dimensional memory device of claim 6, wherein the plurality of the source-side select gate electrodes are laterally spaced apart by source-select-level dielectric isolation structures.
 8. The three-dimensional memory device of claim 7, wherein each of the source-level dielectric isolation structures contacts a respective one of the source-select-level isolation structures.
 9. The three-dimensional memory device of claim 8, wherein each of the source-level dielectric isolation structures has vertically coincident sidewalls with the respective one of the source-select-level isolation structures.
 10. The three-dimensional memory device of claim 8, wherein a horizontal step exists between each of the source-level dielectric isolation structures and a respective one of the source-select-level isolation structures.
 11. The three-dimensional memory device of claim 8, further comprising a source-level isolation dielectric layer contacting a backside of each of the plurality of source layers and comprising vertically downward protruding portions which comprise the source-level dielectric isolation structures.
 12. The three-dimensional memory device of claim 8, further comprising bit lines and drain contact via structures contacting the drain regions, wherein the electrically conductive layers comprise a plurality of drain-select-level electrically conductive layers located between the word lines and the bit lines in a vertical direction, and laterally spaced apart by drain-select-level dielectric isolation structures.
 13. The three-dimensional memory device of claim 7, wherein: each of the pair of backside trench fill structures comprises a dielectric structure or an electrically conductive local interconnect surrounded by an insulating spacer; each of the plurality of source layers contacts only one of the pair of the backside trench fill structures or does not contact any of the pair of the backside trench fill structures; and each of the plurality of source-side select gate electrodes laterally surrounds a respective group of memory opening fill structures and is laterally spaced from any other group of memory opening fill structures of the group of memory opening fill structures.
 14. The three-dimensional memory device of claim 6, wherein each of the source-level dielectric isolation structures contacts sidewalls of a respective pair of the plurality of source layers, and continuously extends at least from underneath a first horizontal plane including top surfaces of the plurality of source layers to a second horizontal plane including top surfaces of the source-side select gate electrodes.
 15. The three-dimensional memory device of claim 1, wherein: the pair of backside trench fill structures laterally extend along a first horizontal direction and are laterally spaced apart from each other along a second horizontal direction; the word lines continuously extend laterally along the second horizontal direction between and contact each of the pair of the backside trench fill structures; a pair of the source-side select gate electrodes extends laterally between the pair of the backside trench fill structures along the second horizontal direction; and the pair of the source-side select gate electrodes laterally is spaced apart from each other along the second horizontal direction by one of the source-side trenches.
 16. The three-dimensional memory device of claim 15, wherein: a pair of the plurality of source layers is laterally spaced apart from each other along the second horizontal direction by the one of the source-side trenches; the source-side trenches overlie the word lines; and the pair of the source-side select gate electrodes is in direct contact with a respective one of the backside trench fill structures and has a respective lesser lateral extent along the second horizontal direction than any of the word lines.
 17. The three-dimensional memory device of claim 16, wherein the one of the source-side trenches comprises a pair of lengthwise sidewalls that laterally extend along the first horizontal direction, are laterally spaced apart from each other along the second horizontal direction, and vertically extend continuously at least from a top surface of a respective one of the pair of source-side select gate electrodes to a bottom surface of a respective source layer of the plurality of source layers.
 18. The three-dimensional memory device of claim 1, wherein one of the plurality of source layers laterally extends underneath one of the pair of backside trench fill structures and is electrically connected to the first ends of the vertical semiconductor channels. 